Very interesting subject. I'm no 'expert', far from it, but I do know that buying any clock, especially old mechanical types, that common sense should prevail, don't let your heart rule your head. A lot of clocks hate being moved and may take quite some time to 'adapt' and settle into their new environment due to handling, humidity and how it is positioned. Pendulum driven clocks have to be dead level front to back and side to side when in their desired position to run properly and when concidering purchase make sure the vendor guarantees it running well and that you can return it if not. Clocks that need repair may need parts re-made which may require the services of the watch/clockmaker/jeweler that could cost more than its intrinsic or resale value. Here where I am located in the UK we have a good monthly antiques fair where a lot of clocks and watches are on offer and although I've not as yet purchased any this way they do seem over priced and some look a little 'suspicious' like they are an assembleage of many and some of the cases, especially the wooden ones, have been polished and cleaned within an inch of their lives. Always, as said, offer the dealer a 3rd of what they're asking and then work up to what you are prepared to pay and it's always a good idea to research and look around the 'net at previous auction house prices that have been achived especially if you're looking to buy a specific type of timepeice. It's the same really in buying anyting, three very important things to consider, condition, condition, condition.