Without doing a bit of re-reading, Whitworth tubes left the foundry as chopperlump, and Kilby one of the few sources for tubesets/tubes? I would speculate Kilby applied the marks as a few examples wear another language than English. Some tubesets have a single number whilst others like the subject double have sequential. I have pondered if the numbers were APUNS. Last, there was a worker strike in 1897/1898 and Kilby produced Krupp steel tubesets for his clients & I think it was Purdey that after the strike offered to replace them free of charge? I'll try to find the thread.
https://www.doublegunshop.com/forum...p;Words=kilby&Search=true#Post322551Serbus,
Raimey
rse
