The Semmerling LM-4 is perhaps one of the most peculiar guns ever produced. This manually operated pistol lacks a recoil system as the slide and barrel are married together. To chamber a new round after firing, you would manually rack the slide forward, which would expel the previous round. Upon moving the slide back to the rear, you would chamber a new round and be ready to fire. This process happens for every round, so rapid-fire or even a double tap could prove problematic.

Introduced in 1979 for a whopping $645, this was targeted as the smallest .45 ACP for concealed carry. The design never fully took off despite concerted efforts to market the gun. In 1982, the company was sold -- including patents and trademarks -- to American Derringer, who would continue to make the odd little gun until stopping regular production in 1998.

It’s estimated that 600 of these were produced with the original Semmerling/Boston, Mass. markings. The one from the vault happens to be especially collectible because of its serial number, #31.

Related: Super Rare Semmerling

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