Okay, here's one for the books. I recently took over a new business office complex. It has 4 seperate buildings in it with 2 floors each building. All glass storefront entrances on the outside of the building. Hopefully you've got the picture now. Oh, BTW WR5 keyways. A tenent wanted an interior lock put on and informed the landlord that he would not be able to be there, but to have the locksmith go ahead and do it. Not a big deal. The landlord and I walked up to the door and his master wasn't working real well. I looked at the door and my mouth fell wide open. Just to prove to myself I went to the van, cut a key and walked back to the door and opened it right up. The landlord asked me how I did that. He and I started walking the floor we were on and I showed him how that previous company labeled the doors (in pencil) with the key cuts. Literally, each door (just above the cylinder) has a 34742 (just an example) written on it.
Needless to say, now the maintenance man is having to go around with an eraser to every door. I've never been so lucky as to be able to recreate a master key system from another company. They apparently wrote them on there so that they could keep up with which cylinder went where, rather than writing it on a set of code sheets.
Just thought you'll might get a laugh out of it. The landlord is still shaking his head over this one.