We know the chemical composition of the gen. It is a Bronze CuSn8 (as previously said basically is 8%Tin and the rest Copper 92%)
If the bronze in rep watch is CuSn8 no worries about colour and patina, we will get completely the same as gen in the rep
With a sample and an Atomic Absorption Spectrophotometer we would get the answer in few minutes.
Some years ago I worked with a Perkin Elmer AAS and was fantastic, precise and fast. Unfortunately I have not yet the opportunity at this moment
If some member has access to such AAS we will be able to know the answer in some minutes
I will try again to get it in Spain. I had no success last year (free cost, of course)
I could also ask for the cost and arrange an account to receive donations from members to get the amount and make the analysis. Maybe, 2-3 Euro for each member would be enough. I would participate with 20€ to start the donation.
ALE