The “laurels” , actually sheaths of wheat, have different meaning depending on who stamped them into the tubes. Actual proof house stamps refer to the level of proof the tubes were submitted to, and passed. You can think of it in the same terms as the old Sears catalog, good, better, and best. A single mark indicates standard proof, two is double proof, and three is triple proof, since 1923. The triple proof mark prior to 1923 was actually 4 sheaths of wheat, for reasons only the French will understand.
The standard proof is, by French law, the highest in Europe, and, really, all that was ever required.
Manufrance was a company that did in house proofing. From where we sit, today, I suspect it means absolutely nothing. Was a gun that got 4, or 5, or whatever number of marks, actually built of a better grade of steel, what was the actual level of proof, who documented that, and what can we learn from that documentation, are all very much open questions.
The proof house gave you exactly what you needed to know with their proof marks. Chamber length, 65 is 2 1/2”, 70 is 2 3/4”, what powder was used, mostly powder T, a modern, smokeless proof powder, since 1900, and metric dimension of the tubes, 9” from the breech, allowing you to measure if the bores have been tampered with. You can figure out what loads you should be using with just those marks. Guns proofed with semi smokeless powders S and J are really just older, the level of proof is right there with fully smokeless powder T. Light loads rule the day in lightweight French guns, and keep them enjoyable to use.
All the other marks are pretty much just boasting and advertising.
Best,
Ted
