Xeo, the key you have is from the
Kirk Key Interlock Company based in the USA.
Kirk Key make key interlocks and interlocking systems i.e. systems that enforce a sequential series of steps via key control. An example application would be the shutdown/start-up procedure of some potentially dangerous machinery. Using a key interlock system a strict sequence of steps can be ensured, thus minimising danger to machinery and/or operators. A more mundane application of their technology is simple trapped key locking systems that retain the key in a required position (open or closed).
The head of the
Kirk Key key is distinctive and forms the design of their logo:
Source:
www.kirkkey.comIt appears you have the key from one their
SD (Standard Duty) interlocks. Your key is stamped
D3 which -- I believe -- is the
key interchange code.
D3 identifies a specific lock in an interlocking system, i.e. there is most likely a
D1...
Dn for a particular system. Hypothetically, to activate system
D the sequence
D1,
D2,
D3,
D4 would have to be
effected. The Kirk site doesn't explain interlocking systems very well but some of their competitors do a good job. Refer
here and
here.
I am uncertain why the key bears the
Yale brand, this does not appear to be a feature of the keys nowadays. I suspect that you have an old key and Kirk Key at one point (they have been in existence since 1932 and have key/lock issuance records going back to 1945) they used Yale cylinders to form their interlocking systems.
[Sandman: Another lock manufacturer for the master list.
]