The length of the cylinder indicates that the OP's revolver is a true Velodog revolver, chambered for 5.6mm Velodog, a long CENTER FIRE .22 caliber cartridge. The term is a combination of "velocipede", an old word for bicycle, and dog. As CornCod says, they were intended for use by bicyclists to protect themselves from attacks by dogs.
Revolvers of the general type were made in other calibers, but most have short cylinders and/or are in other calibers and so are not true Velodog revolvers.
The trigger should not just flop down; there should be a small spring to hold the trigger in the upward position until it is pulled down. Value is nominal, around $100-150 in average condition, though they bring more in top condition. The ammunition is not available except as collectables.
Jim