Geo,
The "silvery part" in the chanel of the action is the main spring on an R model Darne. A Charlin typically lacks this, as it is a completely different design. Further, there is no metal tab under the breech-the stock on a Charlin has to be removed, and a set screw removed from the action pin, which is then driven out with a drift.
"Typically" is a word used in the context of older Charlins, since, the remains of the Charlin company were purchsed by the Darne company around 1955, and Charlins were built alongside Darnes until about 1965. There exist, in very limited quantities, Charlin marked guns that are Darne actions. I've only seen photos of these guns.
Rest assured that a true Charlin, produced by the Charlin company, is a different gun, and a different design than any model of Darne, with zero parts interchange.
Best,
Ted
