The funny Charlin thing is, there doesn't seem to be any consistancy with amount of running bunnies/stars/swallows to grade of gun. I have seen top notch, highly engraved examples that have one bunny, and plain guns that have what seems like a dozen. I have noticed that more fauna seems to be usual on guns with higher levels of proof. My own 16 gauge Charlin had zip, zero, nada grade markings on the flats, just a cryptic LC1. I have several Charlin catalogs that make little to no mention of markings on the flats, but, these catalogs illustrate "Art Deco" era guns, some of them beautifully engraved with almost a Celtic style of engraving. And, I have never seen a Charlin so decorated. Which, is too bad.
Maybe Geoffroy has some insight on the grading thing. Google his name "Geoffroy Gournet" and you could post that question over on his site. But, the truth is, we are all stumbling around many years after the fact on these guns, and documents with hard evidence come slowly, if at all.
Before you go off stuffing a 2 3/4" baby magnum in that gun, do have a reputable 'smith have a look-see at the bores, barrels and chambers. The picture above shows a gun with a high level of proof, rare for St. Etienne guns not built by Darne. P CHOKE usually means full+, in my experience. It left the factory with 2 1/2" chambers.
A Charlin is a pure, over-the-center device, with no secondary locking mechanisms, like a Darne. Firing higher pressure/longer length ammunition will sometimes cause the opening lever to lift out of fully locked battery mode and into interupted mode-if the lever is not closed all the way, the gun won't fire. When you lift the opening lever on your Charlin, even a 32nd of an inch, it won't fire. You can test this, on your gun, without ammunition. But, shooting big number loads in a short chamber gun will sometimes cause the lever to lift sightly, which seldom gives shooters warm fuzzy feelings. I have had several calls over the years that featured excited shooters with freshly soiled pants-it is difficult to calm them down, usually. The gun CAN'T open, at the shot, but, use the correct ammunition for the chambers you have. I have no problem lengthening chambers on typical French sliding breech guns if the 'smith says there is plenty of material. I've never seen a gun with thin barrel walls, either. Oh, and you've probably noticed, that the gun is pretty light in weight-do yourself, your retinas, and your dental fillings a favor, and run lighter loads.
Resist the temptation to dismantle the sliding breech. You need tools to remove it, it is very different than a Darne, and requires little or no maintenance over the course of a century, or so. There are two very small detent balls and captive springs which are very easy to lose-I damn near lost mine, and I knew they were there.
If the Charlin makes a "clunk-clunk" sound when the action is cycled, and the gun is cocked, you have a broken lever spring. I've examined several in this condition. It is an easy fix, and the gun can still be used, but, have it seen to.
The big problem with sliding breech guns of any type or brand, Charlins included, is that most existing guns don't fit 21st century upright hominids, and the difficulty fitting existing guns to those same hominids. LOP changes are managable, but, that is about where it ends. Forget bending the stocks.
You will find that, inspite of being beautiful and unique, Charlins seldom bring any money here in the states. Typically, $500-$2000, depending on condition and grade. They are coveted, and worth more, in Europe, where a guy seen hunting usually has some money. Lots of it, typically.
At any rate, enjoy it. I have had a few Charlins, over the years, and always found that I prefered the mechanics of the R model Darne for my own use, and I no longer own a Charlin. But, that doesn't mean you shouldn't, if you like it. Most likely you have the only example on the block, not that that is always a good thing. For repairs, Kirk Merrington is your man.
Good Luck.
Best,
Ted