[Ghiblicup]

O.k. guys, all interesting; but do we know the composition? Which ever method used to find the composition is fine - but what should specifications be like?
By the way @mickmate -. the tubes are surely not alloy - they are steel. We do have an idea of diamters and thickness, but that could all be reproduced. But nobody can find the same steel today as it was used back then, as steel compositions are changing all the time and get more advanced in terms of tensil strength and other physical characteristics.

I would not have a problem to cut out a piece of a frame in case. With values of these cars going up and up, anything to make sure you buy the "right" thing helps!
On engines, interior, even bodyparts there is no "real" proof. I mean "real" in the sense of 100% certification that the material is genuine. Also because at a genuine car they could have been replaced/exchanged or repaired during the car's life. But not the steel frame!

@rsk289: which were the specs of milde steel the British smelteries delivered?

@CompClassics: Yes Ferrari uses this method, and so does the Mercedes Classic Division e.g. with pre-war SSKs or similar stuff.