Decoding production / chassis build numbers

[bxd]

I recently had a heart-stopping moment…

I was pulling the interior out of my 1969 911T to install a new rollbar (thanks Dave!) and some hard-point seat belt mounts. In that process the seats and carpets needed to come out, and I figured I'd take the opportunity to examine some of the more recessed areas for rust or previous damage repair (that's another story). I took off the rear tunnel inspection panel as part of the carpet removal and for the first time noticed that there was a 7-digit number stamped into the edge of the port (the number is 1297xxx). I know the VIN number stamped next to the smuggler’s box by heart, so I immediately knew that the two didn’t match…I thought “hmm, that’s weird”.

A friend who has restored many SWB cars was helping me with this project and he told me that it looked like a 1969 912 chassis number. I started to get that sick feeling. I then pulled-off the passenger knee pad and found a similar but different 7-digit number stamped there. That number also started with 1297. I was really starting to freak-out…had the car that I’ve put so much time and money into over the past year been crashed or stolen and then clipped?? I then went (ok, I ran) to my computer to see if I could make sense of the discrepancy. I started by looking-up 912 VIN numbers, thinking that I’d need to verify that the seven-digit numbers were, or were not, actual 912 chassis numbers. Here’s where things got confusing.

1969 912 VIN (chassis) numbers DO indeed start with 129, but the next digit is always a zero – never a seven. Plus, 1969 912 VIN/chassis numbers are all either 8-digit or 9-digit numbers – no 7-digit numbers. –So that didn’t make any sense. –As I said, my first thought was that the car had been clipped, and was now a very expensive parts car, but then verifying that there were no 7-digit 912 VIN/chassis numbers in 1969, and nowhere in any VIN/chassis numbers was there a 7 in the fourth digit, I thought, ok, something else is going on here.

I scoured the 912 Reg, Pelican and the Early S Reg for answers and finally found a thread in which someone mentioned that Porsche changed their chassis numbering system in 1969, and that the VIN/chassis numbers in the trunk and on the A pillar no longer matched the chassis build numbers stamped behind the knee pad on the dash.

My rookie 911 owner heart began to pump blood again. The world righted itself and the sky changed from deep red with lightning bolts to soft blue with fluffy white clouds.

As a relatively inexperienced 911 owner, I have learned some valuable information…info that’s probably been posted here on numerous occasions, but I thought I’d bring it up again because it was actually not very easy for me to find it myself. Here’s what I’ve learned:

Porsche did indeed change their number stamping system at the end of 1968. Starting in 1969, for USA/Japan export cars (not sure about ROW), there are 4 locations where the VIN number is stamped or written:
1. Stamp next to the smuggler’s box
2. Silver plate screwed onto front valance
3. Plate riveted onto the inside of driver’s door sill
4. Written in grease pencil on top of the dash, under the dash pad

In addition to this, the number stamped into the dash behind the knee pad became a chassis “build” number, or “production” number. It may or may not match the actual VIN number, in my case it did not, but you may find cars where it does. There may also be other stamped production numbers, like the one I found next to the tunnel inspection port. These may or may not match the number stamped behind the knee pad, in my case it did not.

I have only been able to decode the first 3 digits of these 7-digit build/production numbers. Using my production number as an example, this is what I’ve found:

Production number: 1297xxx
1. First digit represents whether the body is a replacement or standard production – 0 designates a replacement body, 1 designates a production body (not sure what this means exactly)
2. Second digit is the body type and where it was built – 0 designates a Stuttgart coupe, 1 designates a Stuttgart targa, 2 designates a Karmann coupe, 3 designates a Karmann 914/6
3. Third digit is the model year – in this case the 9 represents 1969, a 0 would represent 1970, a 1 for 1971, etc.

I haven’t been able to decode the fourth number, but that position could designate some other main chassis option. –I’m assuming that the next three digits are sequential tub numbers (serial number), but the gurus here should be able to confirm/deny that.

I also learned that if you are unsure if the VIN/chassis number and the build/production numbers are correct for your car, you can send them to Porsche and they will either confirm or deny that the numbers are from the same car. On top of that, I was also told that there is a “secret” 4-digit number stamped somewhere behind the ashtray that can be sent to Porsche as part of that confirmation process, but I have not verified that in any way and welcome any additional info in that regard.

I hope that this saves others from the same horrible feeling I got when I realized that the numbers on my car didn’t match. –And as usual, if what I’ve said here is in any way incorrect, please post the facts so we can all benefit.

[djpateman]

Not quite, but close. For the dash numbers (below radio opening and grease pen )
first digit
0= replacement
1= production body

second digit
0= coupe
1= targa
2= Karmann coupe
3= Karmann 914/6

third digit
9= 1969
0= 1970
1= 1971
2= 1972 and so on

fourth on is the serial number

The tunnel number is a Karmann production number with similar format but an independent series. So a Karmann coupe body could be used for 912 or 911T or 911E, all out of the same series.

I`d really like to know the VIN, dash and tunnel numbers to further my research.

[bxd]

no problem; I'll PM those numbers to you.

Thanks for clarifying those production numbers too

[bxd]

Soooo, what is the difference between a "replacement" and a "production" body?

Was that to discern between a standard car and one that had been completely replaced through some kind of factory warranty replacement thing?

Please explain?

[djpateman]

A replacement body was available through the factory if your chassis was damaged beyond economic repair. However, the car had to be fairly new so that the same body was still in production.

[Limey]

Hi
All, this thread is some years old now but relevant to my current situation. Much the the opening story I have a discrepancy between the VIN (trunk) number and the two numbers on the interior behind dash pad and rear floor vent. The car is currently being restored, and I’m left asking myself ‘do I have a cut & shut’ job or is there truth that there can be differences between the numbers?

Djpatemann maybe you are available for a pm?
Regards
Limey

[djpateman]

I am available now.