I do agree with the general sentiment here. When rebuilding an engine from scrap, it would be a very honest thing to do to date stamp them, but it would need to be done in such a way as to be unambiguous "10th August 2001" not "10/8/01" if you see what I mean. I can see that it would be easy to hoodwink the unwary by the manufacture of enough bits to (say) get a single base casting into running order, especially with engines as they are quite simple devices, if lumpy. But inadvertently? Restoration of an engine might easily require a few castings to be made and machined, valves to be replaced, perhaps a flywheel with a cracked spoke recast.
51% of new bits by number or mass? Very tricky judgement call. Anyway, in a hundred years it will not matter much as the information of the circumstances of the restoration will have been long forgotten. It is impossible to get information on some engines built in the 1950's, let alone
100 years ago!
A friend of mine makes a very comfortable living making medieval coin replicas and especially die sets for striking coins. He is a very skilled man and his work is indistinguishable from the original to my reasonably practiced eye. He is also the very paragon of honesty and works frequently for the British Museum and the Bank of England. He goes to great lengths to ensure that all his work is incapable of being passed off as the real thing and he told me once that all the coins that he sells (and it must amount to tens of thousands in a year) bear the invented name "Grunal", a moneyer than never existed. I grinned at him and said that in a hundred years there
*would* have been a moneyer called Grunal - and look at all the pewter fakes he turned out! His honest consternation was a pleasure to see.
Anyway, to return to the point, it has been truly said that "That which man has made may be made again" and the reconstruction of four early Otto engines is a perfect case in point. If it was me, I'd be trying to do it as well as I could, making the replicas as close to the originals as possible. However, I'd also include a few design features of my own - nothing obvious - but things that would not matter in themselves, but would cumulatively speak loudly to some future purchaser that these were made a century later than the original.
Regards,
Kim Siddorn,