Couple of comments:
1) Canvasback must be right that the arrows through targets are a Manufrance thing. Here is another Manufrance robust with the arrows. I'm going to assume that somehow Manufrance was permitted to proof its own guns and those are the proof marks - double proofed (rather than having the traditional Saint Etienne crossed fronds with a crown). I've seen this speculated before.
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=544373
And when you look at the crossed canon and arrow logo of Manufrance, it seems pretty clear that the above arrow proof mark comes right out of the MF logo.
This conclusion is reinforced by the crossed fronds on the OP gun...without the crown.
I think we can safely conclude that in the 1920's Manufrance proofed their own guns and thus the arrow through target logo. Since they were manufacturing 500 guns a week - or even more - it would make sense....until proven otherwise.
(Conclusion is another first for this site).
2). Here is an English site with an identical 16 gauge gun to the OP. And he's firing slugs out of it.
https://www.thestalkingdirectory.co.uk/threads/16-bore-french-cape-gun.15636/
