Turn out to be a cap gun ! Really fooled me. The coin I was talking about turned out to be a Tombac button.
NICHOLS DERRINGER
This derringer was one of very few Nichols "shell firing" guns - sort of their answer to Mattel's Shootin' Shell line. This one came with three-piece bullets (a shell, a casing, and a red "pellet" tip). The red pellet was the piece that was actually propelled out of the barrel. Though the gun has two barrels, only one is hollow and functional. These days, a single three-piece bullet is worth more than the gun itself.