This is a great little mouse trap from the USA which uses a sideways set of jaws.
When set the two sides of the trap are held open at ground level, hinged and sprung at the top. They are kept apart by a short bait lever, with a tiny raised ‘bump’ that the moving door rests against.
This lever can be baited or the trap just placed on a known run along the edge of a room. The trigger can be approached from either side of the trap and works just as well. The slightest touch will dislodge the finely balanced trigger causing the trap to snap closed.
First patented in 1933, the one pictured here is the modified version patented in 1940. Despite this revised patent, the new traps were still stamped with the old reference.