Lotus Seven Frame and Chassis Numbers

[EdWills]

For Lotus Seven owners or prospective purchasers of a Lotus Seven,  I have added a section "Lotus Seven Frame and Chassis Numbers" on https://anglocanadianlotus7.ca dealing with frame and chassis numbers, plus the estimated numbers of cars built. The article was written with the help of John Watson of the Lotus Seven Register, plus a few recommended books.  John Watson has detailed on his Lotus Seven Registry the locations on the Lotus Seven frame where the frame constructor stamped their build number, before bodywork was added by another company, with Lotus then riveting their aluminium chassis plate with their serial number on to the flat scuttle area.   Hope it is of assistance.  W

[SENC]

17 hours ago, EdWills said:

For Lotus Seven owners or prospective purchasers of a Lotus Seven,  I have added a section "Lotus Seven Frame and Chassis Numbers" on https://anglocanadianlotus7.ca dealing with frame and chassis numbers, plus the estimated numbers of cars built. The article was written with the help of John Watson of the Lotus Seven Register, plus a few recommended books.  John Watson has detailed on his Lotus Seven Registry the locations on the Lotus Seven frame where the frame constructor stamped their build number, before bodywork was added by another company, with Lotus then riveting their aluminium chassis plate with their serial number on to the flat scuttle area.   Hope it is of assistance.  W

Nice work William!  I have one recommendation for making it more valuable - add descriptions (and, ideally, pictures) of locations of the frame numbers across the manufacturers/series/dates.  This question comes up here and on other forums from time-to-time and I think would benefit anyone attempting validate a car being sold.

 

I fully understand John's position on sharing frame numbers, but general identification assistance would be valuable.

 

Henry

[EdWills]

6 hours ago, SENC said:

Nice work William!  I have one recommendation for making it more valuable - add descriptions (and, ideally, pictures) of locations of the frame numbers across the manufacturers/series/dates.  This question comes up here and on other forums from time-to-time and I think would benefit anyone attempting validate a car being sold.

 

I fully understand John's position on sharing frame numbers, but general identification assistance would be valuable.

 

Henry

Hello Henry and forum members above.

Many thanks for the compliment.  John Watson provided a lot of information to me for the article,  I didn't want to duplicate (copy) other information he has previously provided on his web site, so I noted his site in the reference section.  On reflection, I should have mentioned where to find this info! John's 'Lotus Seven Register' has a couple of photos that show the possible location(s) where the frame identification is stamped by the frame contractor. They are shown by clicking the 'register page' and scrolling down. 

 

J.W. does advise that the frame identifier letter/number can be in various locations depending on when the frame was constructed, but there is no mention if Lotus (or the frame builder) ever recorded exactly where they would be located.  Lotus fitters similarly seem to have riveted the Lotus plate in different orientations to fit around the heater for example, but in all of the photos I have seen, on the flat horizontal aluminium sheet in front of the scuttle. Which side of the flat panel would depend on whether it was a l.h.d. or r.h.d. car.  

 

It does appear that the 1" angled steel bracket - that holds the front of the brake and clutch master cylinders alloy bracket - was the location used by Universal Radiators, but J.W. also shows another location on older cars produced by Progress Chassis.   

 

I am guessing, and this is only my guess, that the angled bracket would be easier to stamp before being welded on to the frame. Similarly, the plate that John refers to as being welded on to the frames constructed by Progress, would  be pre-stamped.  It really wouldn't matter what order the frames came off the production line, as the mis-match in frame builder letter/number combinations to the Lotus chassis number combinations reveal.  Some may be very close to each other, some hundreds of numbers apart.  I have only found one Lotus Seven so far that had the exact same builders i.d. number to the number on the Lotus plate. 

 

And just to throw another bit of confusion into the mix, John advised me that the last Lotus Seven Series 3s to be produced were SB2649 a, b, and c.  I queried this, but it seems that as Lotus was at the end of the Series 3 line, someone at Lotus involved with the Series 4, decided (insisted?) that the Series 4 (or IV) should start with the chassis number of '2650'.  With three Series 3 chassis waiting for completion, they were given the numbers SB2649a, SB2649b, and SB2649c.  Not sure how this was viewed by the U.K. vehicle licensing office, but it must have been accepted, as they are fully recorded as individual cars in the Lotus factory records that J.W. has, and were registered for the road.  W.

Edited December 13, 2025 by EdWills

[EdWills]

Hello Henry.

I contacted my pal who updates the web site, and he will add a postscript to my article that provides information on J.W.s site in the U.K.  Thanks for suggesting it.

Cheers, W.