Welcome on your first post. I'm looking at your friend's gun, particularly in the area of the opening lever, and it does not seem like the typical Charlin action at all-more like a model R Darne. Note the difference between the opening lever attachment on this Charlin, and, your friends:
This photo shows the button just forward of the trigger guard that is depressed to get the barrels off.
Please note that it is not as simple as pushing the button-you have to push the button and break the interference fit between the barrels and the receiver. It sounds brutal, but, I usually open the action all the way, hold the gun with both hands, push the button, and jab the muzzles into a piece of masonite hung on the wall for that purpose. Try not to strike the butt plate to attempt to do this, I've seen plenty of Darnes and Charlins with a broken toe on the stock.
The number under the opening lever is the gun's serial number, by the way.
A few more detailed photos of the action, open and closed, the safety, and up by the front of the trigger guard would certainly help.
Best,
Ted