I am convinced that the change from cm to mm dates from 1906-1914, but don't know exactly when. I most doubt that a call to the St-Etienne office would resolve that.


It would be very nice to know when and accessorily why.
The change between CGS system (centimeter, gram, second) to MKS system (meter, kilogram, second) is much later, so I don't think that it plays a role here.
One of the reason would be that a lone "7" looks funny.

I did not know that DD put a date on his barrels.
The first one I know who did this was Bernard, and that is documented in a different thread.
It is important to understand that in the French trade, barrel makers would make barrel sets (with lumps, ribs, etc.) and not individual barrels.
With LB I have documented many cases where there was a significant (years) lapse of time between barrel making and gun finishing.

Final proofing is always the job of the gun maker. But provisional proof is the job of the barrel maker.

So there could be a lapse between barrel dates and final proof dates.

The use of T powder is also questionable. MF used S powder proofing much after 1900. Sometimes multiple proofs were done at the same time. I have a Pirlet gun with PJ, PS and PM marks.

All the best...
WC-