Thanks. I tracked down a handcuff key during lunch hour and struck out there...not the right kind of key. After work I'll take a shot at finding a key that fits...I swear the hole looks familiar. If no joy is found down that route I'll take a stab at picking it.
Have a look at Florida Time Clocks, supposedly thye carry Lathem stuff...http://www.floridatimeclock.com/index.htm
If its a round keyhole, it could be a Detex-type key.. Florida Time Clock has those..