When the Massachusetts Arms Company initially produced the Wesson & Leavitt Dragoon revolver, they quickly incurred the wrath of the colt company. Those initial revolvers violated several Colt patents. The resulting lawsuit forced the end of production of the Dragoons, and the company decided to redesign the guns to avoid the Colt patents. The result was this .31-caliber belt model revolver, as well as a similar .28 caliber pocket model.
To make the guns legal, the hammer was no longer connected to movement of the cylinder. Instead a release button was located inside the trigger guard. After firing, the user would press this to release the cylinder and then manually rotate it to the next chamber. In addition, the metallic cap priming was replaced by a Maynard tape system (used under license, unlike the Colt patents!).
Not more than about a thousand of these revolvers were made, as they were obviously technically inferior to the Colt guns of the time. However, the small sales, combined with other guns, were enough to hold the Massachusetts Arms Company above water financially until 1857, when the Colt patents expired.