Found a couple of interesting Francotte guns

SN 32145 c. 1898. Siemens-Martin barrels with 2 5/8" chambers and not Nitro proved

[Linked Image from photos.smugmug.com]

VL&D marked 10g SN 33751 c. 1900. 4 Iron Damas Crolle with 2 7/8" chambers

[Linked Image from photos.smugmug.com]

Both have 2 sets of muzzle over bore dimensions.
Belgian First Obligatory Proof for “Double-Barreled Breech-Loading Sporting Guns” was for breech plugged tubes. The barrels were marked with the bore (often overstamped at 3rd Proof) and received the script EL provisional proof mark.
Second Obligatory Proof was for joined barrels, fine bored and finished; likely the first set of dimensions
Third Obligatory Proof was for finished barrels attached to finished action and likely the second dimensions typically with a slightly larger bore

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