Instead, a combination of evidence in the shape of unrestored bikes found over the years, and deduction based on known factory practice is used. Most owners are restricted to one example to analyse but when this is multiplied up several times the findings are much more forceful. Common sense dictates that later parts found on a bike tend to imply owner modification, especially if they are more than one year later, whereas finding parts from the previous year on your bike is far more likely to be correct. For example, with a 5H registered in 1937, with a 1938 engine number but sporting mudguards and inner primary chaincase from late '36, with only one owner and unused since the fifties, all the signs are that the early mudguards were fitted at the factory as they would have been much harder to obtain later.

Triumph were well known for minimising waste and using components and finishes that were expedient at the time rather than slavishly following the catalogue spec on every model within that seasons production. Especially with components bought in from companies like Lucas. The inspection lamp in the tank-top instrument panel sometimes changed in design within each year according to the availability. This is entirely logical as it clearly wouldn't be worth holding up production for such a detail. Similarly paint finishes were not clearly delineated by year. See 'Paint'.

By also looking at registration dates, together with engine and frame numbers, a picture emerges of the construction, finishing and selling process which fluctuates considerably, adding to the tendency of models overlapping into previous and subsequent model years in their specification.

I've found several very original examples. In particular a 1939 6S that was totally original having never been dismantled. However, the excitement of the find is soon tempered with the realisation that either: The remains of the original finish must be endured along with a patina that, though interesting, is not what it used to be. Or, even worse, must be lost forever to apply a new finish. Most of us have suffered the disappointment of receiving a delicate, engraved casting back from the platers, with all the detail ruthlessly polished off it. The 6S retained all of its original equipment, right down to the last detail, including a sticker inside the toolbox telling the new owner to fill in the guarantee. It had had one owner, a civil servant, with no mechanical interest. He had run it for about fourteen years and had never done any dismantling. 90% of the paint was good (it was a black finish). With only a good clean on dismantling, the magneto rebuilt, most of the rubber replaced, and the front wheel respoked, it ran fine and was a delight to use. Transfers, engraved instructions, petrol piping, battery connectors and all those special small parts that are usually discarded by the impatient owner were all present. The rubber covered wiring loom was carefully plaited along the top rail of the frame, the tiny sprung ring on the girder fork spindle to stop the butterfly nut spinning loose was still there, old tax discs, handbooks, the lot. Most interesting of all, each nut, bolt, screw and washer lay undisturbed. Virtually all were special. There were perhaps six to ten plain bolts on the entire machine. The rest were either shallow hex, radiused head, small hex to shank, shouldered or something clever. It is this extraordinary attention to detail that contributes so much to the overall beauty of the machine. For instance, the quarter-inch bolts securing the headlamp struts to the fork had shallow, radiused heads with no washer to visually reduce their prominence. On the inside, the nut, too was radiused and the end of the bolt radiused again to match the nut perfectly when it was tightened. Surely a standard of finish that must have surpassed nearly all other manufacturers

If I took the expensive and painful route of completely refinishing I was going to destroy this charming relic of the past. Clearly there were cases for conservation in the shape of the old 6S and a candidate for restoration must be something different. Nevertheless, it was a thorough benchmark reference point for every part of the machine, most of which would apply to all models in the range.

So what is the committed enthusiast to do, who wants exactly what those young men in 1938 saw when they gazed at the bikes in the shop?

There are too many badly restored Triumphs already. A close look reveals hundreds of shortcuts and misconceived attempts at simulating the original specification. Powder coated paint, thick as treacle and blurring the detail of all the castings, off-the-shelf exhaust systems hanging at awkward angles. Cheap, imported saddles and so on. But this is not a restoration, it's an approximation. An attempt to simulate the original using a confusing mixture of parts and finishes governed more by what was available at the time, than anything else. Perhaps most telling are the attempts to reproduce the horseshoe-shaped, painted panels on the sides of the petrol tank. This requires a sympathy of line which seems to defeat most. It was conceived by the designer in a very particular way, to carefully echo the surrounding forms of the base of the tank, the top panel and the kneegrip and as such, follows them in a parallel line as far as possible.