Thoughts from Robert Champ
Sunbeam numbers do tend to have a legibility problem on curved surfaces, particularly on bicycle frames and noticeably when the more complex post-1933 numbering system was introduced. Hand-stamps, for obvious reasons, could not be used with much force on frame tubing or alloy crank-cases and many were only partly legible when new. Marstons, it must be said, was a careful company and their records were comprehensive, judging by surviving samples; we can only regret their loss, probably at the time of the BSA group's closure in the 'seventies. Some other motor-cycle companies were much more haphazard.
As many members will know, the frame number on machines with two-stud gearboxes is usually stamped into the steering head and also on the top surface of the casting above the gearbox, normally above the holes for the rear engine-plate bolts.
When buying a Sunbeam of this era, it is wise to check that both of these frame numbers agree; many of the steering-head numbers were obliterated when a substitute frame was being used, or they were altered to give the 'right' frame letter. The rear-frame number is often ignored in these cases. In any case, back in the 'sixties when our machines were getting their first re-build, no-one checked and many bikes were built around the best frame available, rather than the correct one!
Always check that the machine's numbers clearly agree with the documents. Prefix letters and numbers were not always written on to the old R.F.60-style Log Books and may well be absent from V5 or V5C equivalents.
Why bother? Well, the DVLA is becoming more pernickety, as some members will already know and this tightening of attitude is, or ought to be, reflected by traders. Certainly, if a frame number cannot be found, this has to be declared by an auctioneer, usually to the detriment of the price, and it should equally be declared by any dealer or private seller, since the new owner of an un-numbered Sunbeam risks being given a 'Q' plate as a 'special'.
A useful tip is to make sure that your numbers are not hidden by thick paint, grease or anything else, since, to put it simply, the bike is worth much less without them. High-lighting the frame numbers with white is a useful idea.
Engine numbers have their own difficulties. A quick glance at any list of Sunbeam numbers will show that the 'batch number' prefixes e.g. 145 / 95900 are frequently combined with the number to give 1459500 or missed out leaving 9500, neither of which tallies well with the existing records, themselves the number series made available by Sunbeam in which the prefixes were absent anyway.
Assuming that the number is clear, record it accurately. Sunbeam engines, gearboxes and frames, in my experience, are always numbered. If there isn't a number or the letter shapes ( or typeface; Sunbeams do not seem to have adopted 'new' typefaces ) is not 'right' , be suspicious.
The problem is that there is a great degree of interchangeability between engines and frames in the pre-Burman era so what the antique trade calls 'marriages' are common. The TT frame in the September 2010 issue shows this clearly. I am jealous..
Bicycles are bliss, of course. They only have one number and are easily datable to within six months or so. But that is another story.
If in doubt, check with Paul.
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