Call Elliott Brothers 336-722-2174. They are 3rd generation locksmiths. Two of the older ones are still working- they probably can tell you.

One lock was used when you expected people with keys to come by during the day: milk delivery, maid, etc. It kept out the riff-raff

The other lock used keys that only the family had - to keep the milkman and maid out when they weren't supposed to be there.

That is SO cool, Lazygardens! Thanks for the information!!!!

Anybody know the lock companies name that made the two hole skeleton key front door locks??????

Corbin Ceylon B-11300 is one make-model sometimes referred to as a double bit.