chubbbramah wroteThe lock alluded to by Halflock is probably the lock by Burg Wachter originally designed as a keyhole-blocking lock for blocking the keyholes of locks using a bit key - common in Europe.
This key design goes back some way further though: for example, it was used for the steering lock of early post-war BMW m/c’s. It’s a small (typically 3 or 4) pin tumbler cylinder.
The same design was also used by other makers; I have a key for a furniture lock distributed by Hafele. So european, late 20C.
My memory was in ERROR. The BMW m/c steering lock was a flat pin tumbler key.
However, keyhole-blocking locks are indeed still made. And yes, Burg Wachter still supply, here’s from their US site:
http://burgwachter-usa.com/safe/products/locksAndBolts/security_inserts.php
I have several blocking locks, by various makers, used for furniture locks, sliding doors of several types. Several of the keys are very short, covering only 2 pins, though the locks have provision for 4 pins.
Incidentally, the keyhole-blocking lock idea was invented by Sampson Mordan in 1830. He used a Bramah-type key mechanism for his ‘lock protector’.
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