If there's a C above the serial number on your Mongoose, the bicycle was probably made in early 1976. Look for a letter and number in addition to the C above the five-digit serial numbers. In May 1976, BMX Products began including a letter and a number with the C. The additional letter indicated the month the frame was produced. Hopefully you can find the serial number on the bicycle you're looking at, email if you're having trouble. Bicycle Serial Number Chart. Serial numbers All bikes all have unique serial numbers. Most bicycles have their serial number engraved beneath their bottom bracket, but sometimes serial numbers are found in other places. For example, the serial number 1355592 on a 1975 bicycle. The reverse has not been documented, so it is likely that bicycles are no older than the first digit in the factory serial number, but could be younger. Sometimes local bike shops etched serial numbers into the rear dropout, but this number may or may not match the original.

  1. BEESTON HUMBER FRAME NUMBER DATING. ELSWICK HOPPER FRAME NUMBER DATING. The following dated bicycle frame numbers from the Singer Car Club (not guaranteed): 1903 – 142069. I started to collate frame numbers from 1890s-1920 Triumph bicycles, and will update it.
  2. Picked up a Nitro and it has the serial number sy6g000016. Owner didn't know the year but from pics I've found it looks to be a 96 or 97, with the 6's in the number I'm leaning towards the 96.

By Year/Model

Redline Squareback

First production bike was serial number 100. A low number bike would be early 1974.
By the 500-600 range somewhere begin the 1975's.
1974-1975 Front gusset had no hole
1976-1977 Front gusset had two holes

1978-1979 MX-II - 4130 frame/fork. Used the Squareback front end & the now familiar MX-II rear end on early models.

1978-1979 Proline - 4130 frame and fork.

Japanese made frames started in 1979
RI 79
RJ 80
RA 81
RB 82
RC 83


RJ 09623


1981 700 MX-II 4130 frame & down tube decals, Vbars & Redline stem, Suntour VX alloy 3 piece cranks.
1981 600 MX-II 4130 frame & down tube decals, Vbars & Redline stem. Only difference from the 700 is the 1 piece
1981 520 MX-II 4130 frame & down tube decals, Vbars but cheapo slant stem & Coaster brake Tuff Wheels.
All three came in your choice of Red, White or Blue.

1981 700 MX-II 4130 frame & down tube decals, Vbars & Redline stem. Sugino Maxy-Cross alloy cranks, Suntour seat clamp & hubs, National skinwalls & KKT alloy pedals.
1981 600 MX-II 4130 frame & down tube decals, same as 700 but came with Sugino 4130 1 piece cranks & KKT steel pedals.
1981 520 unknown specs.
All three came in only Blue, Red, Black & White. Chrome would come to the lineup in spring of 1981.

Late 1981/1982
The new bikes appear in the Oct. 81 issue of BMXA. Since the Advertisement had to be shot & submitted before print deadline it probably means the bikes were out at the end of summer of 1981.
They feature the long huge Redline logo in red with white or black trim. As in the earlier years no decal Identifying the bikes as 600 or 700 etc is on the bike yet. The new blocky RL logo is on the seat mast sides & headtube.
1981/1982 PL-20 Carrera uses a Proline frame, flight cranks & still using Vbars.
Available only in Chrome at first with red or blue parts packages.
1981/1982 700 Now using a first generation MX-III frame which is really a MX-II. Sugino Maxy-Cross cranks. Everything else same for 600.
1981/1982 600 Now using a first generation MX-III frame which is really a MX-II. 4130 1 piece cranks.
Both available in Chrome, Red, White, Blue or Black.

MX-II vs. Series-III
Early MX-III were the designation for complete MX-IIs from Japan. The first MX-III frames confused people so Redline also called them Series 3, ST(as in ST-20), Series Three etc.
Late 1982 the first Series-III based bikes rolled out the 600a & 700. Here is how to tell if you have a MX-II or Series-III based frame. Bottom Bracket height(center of BB to ground)MX-II, 11 3/8' . MX-III, 10 3/4' Remember wear & tear on the tires and tire design will affect the BB height slighty.
MX-II Top Tube(TT)is 18'
MX-III Top Tube(TT)is 18 3/4'
MX-II weighs @ 4 lbs 8 ounces
Series-III weighs @ 4 lbs 1 ounce(Dont forget to weigh clean with no headset or BB cups in.)
Series-III have larger then normal drilled out holes on the BB(4 holes)& HT(2 holes), which are covered up by the main tubes.

1983 versions of the MX-III bikes were set to arrive in showrooms, October 1982.
Was the first year of the Redline MX-III. Well sorta. Till then all MX-III series used a MX-II frame according to an interview by Len Weed from BMX Action Dec. 82. Linn Kastan stated in 1983 Redline debuted its first real MX-III. It came as a complete bike Models 700 & 600a & Frame set.
First year the complete bikes had the model (600a etc) on the frameset.
Specs. TT & DT outside diameter was 1 1/4.' Forks 1'. Wheelbase was around 36' BB height was 10 3/4'.
1983 700 - 4130 came complete with Sugino Maxi-Cross cranks & Redline stem & Vbars.
1983 600a - 4130 came complete with Sugino 1pc or Sugino GT 3 piece cranks, Mild steel Kusuki Vbar & Sugino alloy & 4130 stem.
Both available in Chrome only. Your choice of black or blue parts.

1984 500 A - 4130 Series III frame set(MX-III). Sugino 175 1 piece cranks. Red to Yellow fade decals.
Available in White or Chrome only. (Made in Taiwan)
1984 600 B - 4130 ST-20(MX-III? ST as in Series Three as in MX-II?)104A forks(A as in all weld instead of the three spot?).
Available in White or Chrome only. Black with some grey background down tube decal with red Redline. ST-20 on seat tube & not 600b. Vbars & same pads as the 700P. Mostly black with some grey & red Redline written several times.
1984 700 P - 4130 Proline frame, same frame that the Carerra comes with. 101A Tapered forks.
Available in White or Chrome only. PL-20 on seat tube & not 700P. These use a Red to Yellow fade. Bike has 1 piece Sugino 175 cranks.

1985 500 B - Tri Moly. 4130 front, mild steel rear triangle. MX-III type frame. Fully painted finish or all chrome. Econo stem.
Available in all Hazard Yellow (not partial Chrome like the 600 C) or Chrome.
1985 600 C - 4130 Front was painted or chrome, rear was chrome. MX-III frame. Forklifter stems. 1 piece cranks.
Available in Hazard Yellow, White or Chrome. Parts all black & chrome. Rear dropouts are gnurled. (Made in Taiwan)
1985 800 P - 4130 Proline frame & fork. Forklifter stems. 1 piece cranks.
Available in Turquoise/Chrome, Yellow/Chrome & White/Chrome


1987 400 C - Tri-Moly?
1987 600 CXL - Available in White, Red or Turquiose

1988 400 C - 4130?, Available in Chrome, Inca Red, Jaguar Black, Kiwi & Mango. Series-III frame
1988 800 PXL - 4130, Available in Chrome, & a Red & Jaguar Black. Proline 2 frame.

1989 390 -
1989 400 C -
1989 400 D -
1989 700 EXL - Retro Inspired logos & Proline tapered type forks, 180mm 1 piece cranks.
Available in Red, Blue, Black & Chrome.
1989 800 PXL -


Blue=Pacific Blue, Red=Rio Red, Yellow=Solar Yellow, & Gray=Carbon
Color was front end with Gray or Chrome the back end.
1990 Three (300) - 18th Anniversary model, uses a Series-III type frame.
1990 Three (390) - 18th Anniversary model, uses a Series-III type frame. MX-II type forks.
Available in Red/Gray, Blue/Gray, Yellow/Gray & Black/Chrome
1990 Four (400 EXL) - Series-III type frame. TRX Type, leading axle, dropout forks.
Available in Red/Gray, Blue/Gray, Yellow/Gray & Black/Chrome
1990 Seven (700SL) - Proline type frame. Proline type forks.
Available in Red/Gray, Blue/Gray, Yellow/Gray & Black/Chrome.

All Have commemorative sticker stating 1972-1991
1991 320 -
1991 420 - Available in Chrome, Red, Yellow or Blue.
1991 520 - Tri-moly frame. Tapered Proline 4130 forks.
Specs: TT-18 1/4', WB-35', BB-11 1/8', RE-15 1/2', TT OD 1 1/8', DT OD 1 1/4'.
Available in Yellow/Gray, Blue/White, Red/Gray(or Chrome)
1991 720 SLX - Available in Yellow/Black, Red/Black, Blue/White(White or Black being the back end color)

1992 Redline Platinum - 20th Anniversary Edition. Only 50 made. Browning front suspension.

1993 RL 340 -
1993 RL 440 -
1993 RL 540 - 4130 frame/fork. Two tone paint & chrome finish.

By Serial Number
Early USA made bikes may have had a code like this:
RA = 81 Then run number is 5 digits.
RB = 82
RC = 83 etc...

**However bikes in the Museum throw that formula in the trash** (I will leave it up for now. The second letter may mean something, but its not the Formula people have been saying.

RA 04320 - 1982 Redline MX (Made in Japan, Redline Hotdog stamp)
RB XXXX - 1982 Redline MX-II
RB 01382 - 1984 Redline 102b (May possibly be a 82 or 83) (Redline Hotdog stamp)
RB 01693 - 1982 Proline II (has No gusset behind seat, CS bridge)
RC 01878 - Unknown Year, (maybe 600a) MX-II or III (Redline Oval stamp)
RC 06430 - 1984 Redline 600b
RC 07870 - 1984 Redline MX-III(ST-20), (has gusset behind seat, Redline Oval stamp)
RC 07631 - 1984 Redline 600b (Redline Oval stamp)
RC 09325 - 1984 Redline Proline (Redline Oval stamp, CS bridge)
RC 09858 - Unknown Year, Redline Proline (has NO gusset behind seat, Redline Oval stamp, CS bridge)
RC 13645 - 1984 Redline 700p
RE 00533 - 1985 Redline 800p
RH 00726 - 1983 Redline 600a (Redline Oval stamp, NO CS bridge)
RH 07118 - 1983 Redline 600a
RH 00250 - Unknown Year, Redline 102b
RI 0394X - Unknown Year, Redline MX-II or III (claims top tube is 17' but they only came in @18 & 18 3/4)
RI 05788 - Unknown Year, Redline MX-II or III
RJ 00829 - Unknown Year, Model
RJ 02630 - Unknown Year, Model
RJ 03295 - Unknown Year, Model
RJ 05818 - 1980 MX-III (MX-III was a MX-II frameset sold as a complete bike that came from Japan)

RJ 09623 - 1980 MX-II/MX-III

9 Digits, Letters & Numbers
WA9F01870 (1999, June)
WN0C05414 (2000, March) Redline 340
WN0C07804 (2000, March) Redline 340
WV9G05080 (1999, July)

The third number appears to be the year in this case 1999. The letter that follows that may be the month.
This is speculation based on the bikes age.

Someone posted a RMCF80257. Perhaps the C was actually a 0, then it would fit in with the above structure more.

Bmx bike serial number lookup

8 - 7 or 6 Digits year stamped
866814 1986 Redline 500c (Redline Oval stamp. Trimoly stamp)

8609340 1986, September, bike number 340. Or maybe a typo & it is supposed to be 8 digits.

85021290 1985 Redline 600c
85050047 1985 & 05 the month
92081262 1992 & 08 the month
92081370 1992 & 08 the month

6 Digits
Some bikes have the Oval Redline stamp & some dont.
Speculation is that if it has the stamp it is made overseas. That isn't confirmed.
118468 (No Info)
341200 (No Info)
346386 (No Info)
370904 (No Info)
373568 (No Info)
494904 (No Info)
496287 (No Info)

109891 1984/85 Redline Proline (700p or PL-20) Frameset

**It is my opinion that these bikes were simply stamped in order, with no date coding put into them. The lower the number the earlier it was made, starting in 1979. Some model years started earlier & this throws off the fluid look. Also some bike owners may confuse the year of the date it was originally purchased with the model year which in some cases could be different**

340790 1980 Redline Proline (PL-20)
341692 1978-80 Proline (has No gusset behind seat, No Redline stamp)
343277 1979 Redline MX-II (has No gusset behind seat, No Redline stamp)
348647 1982 Redline MX-II (600 or 700) Frameset.
349470 Unknown Year Redline MX-II or III
350291 1981 Redline Proline 2 (had No gusset behind seat, & No CS bridge)
350294 Unknown Year, Redline Proline
354065 Unknown Year, Redline MX-II
357485 Unknown Year, Redline Proline (No CS bridge)
363127 Unknown Year, Redline Proline (Redline Oval stamp)
375830 Unknown Year, Redline Proline 2 frame (has gusset behind seat, CS bridge, Redline Oval stamp)
375996 1982 Redline Proline 2 (has the gusset behind seat, CS bridge, Redline Oval stamp)
499612 Unknown Year, Redline MX-III frame
502365 1984 Redline MX-III frame (has gusset behind seat, CS bridge, Redline Oval stamp)
502867 Unknown Year, Redline Proline (CS bridge)
505092 Unknown Year, Redline MX-III frame (has gusset behind seat, No CS bridge, Redline Oval stamp)
507159 Unknown Year, Redline MX-III frame (has gusset behind seat, No CS bridge, Redline Oval stamp)
510537 Unknown Year, Redline PL-24 (CS bridge)

5 Digits
08453 1978-79 Redline Proline.
15188 Unknown Year Redline Microline

Assorted Codes

Giant Made
Giant made should have two separate code areas, 1 on each dropout.
G0684 (on one side) First two digits are month, last two digits are year.
4673620 (on the other dropout) Run number

G0684 4673620 Giant made, June 1984
G0684 5676717 Giant made, June 1984 1984 Redline MX-III (Redline,Hotdog stamp

R88041521 - 1988 Redline Proline (800 PXL - April, 1988)
R87112584 - 1987 Redline (November, 1987)

85 RL REO 03155 (1985, Redline, Built by Code, run number) ???

DBSN 401Q7687 (Built by code, came with 401's, Q cause they look cool & run number) ???
Or did he write it down wrong was the Q actually a 0? That would work with the below bikes sequence.

DSRM 40110554 This bike is a survivor. Owner cant remember the exact year but it was 1984/1985ish. It is a white 500a.
The 500a used a MX-III frame. Well the owner thinks it may be an 1984 & the code starts with 4 so maybe that was the year & the 01 is the actual month. the rest 10554 could be the run number.

DSRM 40555038 Only certain info is it is a MX-II or III frame.

DJBM 4020463 Perhaps 4 is 1984 & 02 is for February.

**Sure looks like the 4 is for 1984 & the 01,05 etc for the month, with the run number following**


Third digit is last digit of year. The 4th digit is most likey the month of production.

IS7K0384 1997 Redline Cruiser (The bike seems to also have date codes on the seat tube & forks)
IS7J0211 1997 Redline 20

ACX0G0461 Unknown Cruiser code. 0 may be for 1990 & G for July.
ACR2K00### 1993 Redline RL340 (Serial number stamped on BB)
ACR3A00### 1993 Redline RL340 (Serial number stamped on BB)
ACR4J05213 1994 Redline Cruiser (Serial number stamped on BB, Redline Oval stamped)
ACR5B00094 1995 Redline Cruiser (Serial number stamped on BB, Redline Oval stamped)

RLW0050#### 1991 Redline RL320 (Serial Number is stamped on seat tube)

RMCF802527 Unkown Year, Redline RL 340 [1 1/8 head tube]
RMCH023215 Unknown Year, Redline RL 340 (perhaps H is for August & 02 is the year)
RMCH00287 Unknown Year, Redline RL 340 [1 Inch head tube] (since these two appear to be numbered same series but one has 1 less digit a error reading the serial numbers may have occured)

L90050069 1990 Redline Proline (700) (Full Chromoly stamped and Redline Oval stamped)


Will try to dig deeper. If you can add to this, make corrections please do.
Unfortunately almost no one posting serial numbers posted pics or posted bike that posted the serial number.

Vintage Diamondback Bmx Serial Numbers

Gork Informed me Redline has no Records of those early Invoices or Serial Numbers.