I don't know if it's worth buying but somewhere here in these pages I saw lever lock impressioning instructions that were good enough to help me make a workable key for an antique bedroom door. A former co-worker has a really old house that she wanted to turn into a bed and breakfast. She felt (rightfully so) that leaving the authentic locks in place would add to the character. I'm sure the key I made up looks nothing like the original, but it works and it's not too terribly ugly.
If you do splurge for it, let us know if it's any good. I'm always looking for interesting stuff to read on the commuter bus to freak out the other riders.