Volley pistols.
The top one is a percussion (caplock) made by Henry Harrington, Southbridge Massachusetts, c. 1840. It fires 7 .12 cal bullets simultaneously, and has multiple interchangeable breechblocks for rapid reloading.
The other one is by Giovanni Merolla, Italy, about 1860. It is .22LR. Each hammer fires 4 barrels, both can be fired simultaneously.