Tubeset possibly knitted on V-C's chopperlump variant?:



Canvasback:

I'm going to hazard a guess the MI Bloc is MODE Intgralbloc.

c'est le demi-bloc intgral ou intgralbloc

http://gravure.blog.fr/2011/03/28/la-fabrication-des-canons-a-saint-etienne-suite-10904999/

The pin configuration points to a back action sidelock variant. What is odd is the issued serial number.



Kind Regards,

Raimey
rse