You guys may find this interesting. I recently purchased a 250 that I was told had been "serviced." I had no reason to doubt it. The movement was a bit slow, but generally worked ok. Every now and then there'd be some massive hiccup, though. One day would be minutes and minutes off. It was strange. Chalked it up to lack of wear -- if it sat, it didn't keep good time. If it was worn, it did ok. WRONG!
Get a load of what Zig had to do to get this movement working properly.
"Movement completely disassembled. Various problems noted
Pallet fork end was bent up, straightened out
Pallet stones were loose and the exit stone was not adjusted correctly, the escape wheel was dropping on the impluse face instead of the locking face. Exit pallet stone adjusted correctly. Both stones cleaned of defective shellac, new shellac melted on stones, secure now and adjusted correctly.
Movement was dry with very little lubrication anywhere.
Center seconds hand tube was defective, the tube pulled off and separated from hand when removed. New tube fabricated and riveted to hand, re-installed."
Unbelievable. It just goes to show again how much time and attention he spends on these things. It's now ready for years of trouble-free operation.