pics 1 and 2: UMNP-1, mechanical fuse pressure/pull type
pics 3 and 4: UMNOP-1, mechanical fuse pull/pressure/release type
on UMNOP-1 trip wire can be attached to one of two pins, and pull either axial either under 90deg to fuse axle.
pics 3 and 4: UMNOP-1, mechanical fuse pull/pressure/release type
on UMNOP-1 trip wire can be attached to one of two pins, and pull either axial either under 90deg to fuse axle.