Abstract: A lock with a keyed removable plug having a substantially cylindrical body, and a plurality of tumblers disposed within the body and movable between a first position retracted within the cylindrical body of the plug and a second position with one end extending from the body. A retaining tab extends radially from the plug body at an angle from the radial orientation of the tumblers. A shell has a substantially cylindrical opening therein for removably receiving the plug in a first shell end. The shell further includes an annular shoulder spaced from the first shell end and engageable by the plug retaining tab and a retaining one of the tumblers when in its second position. Tumbler grooves extend axially along the sides of the shell opening from the first shell end to a groove end short of the shoulder, and a release groove extends axially along the shell opening from the first shell end to the shoulder to define an opening in the shoulder.