Nagant revolver. Russian gun that has a unique gas seal feature for the cylinder--it's designed to slide forward against the forcing cone, so there's no cylinder gap. The trigger pull is really heavy in double action because the spring has to move the cylinder, though there's some things that can be done to reduce it. The seal feature makes it the only revolver that can truly be silenced. The KGB is said to have liked it for that reason.

I owned one for awhile. Shot fine, but was since traded.