there are alot of lever type mortice locks that take keys like that. Usually, they can be used from both sides, which half explains the symmetry of the key.
For the point of the exercise, i'll use
this picture for reference. And the locks that i'm talking about look like
this lock.
The left hand highest cut is the bolt throw. The next three steps beside it are the three cuts that operates the levers. When the key is inserted from the other side, the right hand highest cut operates the bolt throw, with the three cuts to the left of it operating the levers.
When the key is inserted, only one half of the key is actually used to retract the bolt mechanism. You don't see these type of locks on new houses these days, since other more secure locks, i.e. knobset / deadbolt configurations or deadlatching mortice locks are much more reliable and easily rekeyable.
And on that note, these locks arn't rekeyable. There are some types of mortice locks that only have wardings that stop other keys from entering the lock. As such, in a particular lock series, they may have 40 different lock warding combinations. Which means that if you have a lock that takes key #27, and someone else has a lock that takes key #27, his key will work your lock. To stop a key from working the lock requires replacement. Like I said, they're being replaced by more secure locks.
At work, if we have to secure a door with one of these locks on it, we usually install a conventional deadbolt on the door and remove the mortice lock's locking bolt.
My thoughts are that the 92 is the key/lock number.
/deposits my $.02c in the LP101 piggy bank.
