Help identify part on Shotgun

[Pronghorn19]

My friend recently just bought a single shot shotgun with the name "Cherokee" on it. On the shotgun is this little circular compartment near the hinge. Does anyone know what it is, or what purpose it serves? I have not seen the shotgun personally, but he claims that there is no screw under the hinged piece. Can you help us out? Thanks!

Also, if anyone knows anything about "Cherokee" brand shotguns, I would love to learn a little history on this interesting piece.

 

[PRD1]

That little trapdoor...

is almost certainly the takedown key - that is; in order to detach the barrel, you open the 'lid', which then becomes the 'handle' by which the hinge pin can be unscrewed, allowing the barrel to be removed from the frame.
PRD1 - mhb - Mike

 

[rcmodel]

That is exactly what it is.

Open the thumb-screw finger piece and unscrew the hinge pin with it.

Use some penetrating oil on the hinge pin on both sides and don't get over-zealous trying to unscrew it with a wrench or pliers.

You can break off the thumb-piece if the screw is rusted in.

Cherokee Arms Company: Trade name used by the H. & D. Folsom Arms Company on shotguns.

rc