colt m1877
The Colt Model 1877 was a double-action revolver with very similar dimensions to the more famous Colt Single Action Army, though can be visually distinguished by its larger trigger guard and curved handle. It was a favored weapon of figures such as Billy the Kid, John Wesley Hardin, and John Henry "Doc" Holliday.
Despite users of such pedigree, the Model 1877's double-action system was extremely delicate and frequently broke, turning the gun into a single-action where the hammer and trigger had to be manually operated. Much like the SAA, the Model 1877 was never made capable of using smokeless gunpowder, and late in its life had to carry large warnings to use black gunpowder only.
In anime, the Model 1877 is most commonly seen used by Billy the Kid in Fate/Grand Order.