This style of key fits many of the slightly older Casio cash registers.  The program (PGM) key will enable you to access every position on the key lock.

Compatibility: 

Casio CE-3400, Casio CE-3500, Casio CE-3700, Casio CE-4000, Casio CE-4500, Casio CE-4600, Casio TK-1200, Casio TK-2100, Casio TK-2200, Casio TK-2300, Casio TK-2700