Some interesting finds this evening.
Older readers may remember the self-winding, centrally-synchronized Western Union clocks, big clocks (face 14" or so in diameter), often with a square wooden case, bearing the company name and proud assurance, "NAVAL OBSERVATORY TIME," often over a red lighting bolt just so you wouldn't miss the point. Radio stations used them, if they could afford the service, (sometimes leading to surprised announcers if the clock was a little off when Western Union sent the synchronizing impulse and the thing skipped ahead during a station break!) and they weren't too uncommon in offices and shops.
They're still around -- they were built to last -- and Ken's Clock Clinic specializes in fixing them. The clocks typically used a couple of big old #6 dry cell "batteries"* and he offers both straight-up replacements for the dry cells and nifty versions that use modern electronics to provide the synchronizing signal, too. (Alas, his repair bench is very busy -- but he does have a waiting list).
Those #6 dry cell replacements are of interest to old-radio folks, too (and even antique telephone hobbyists, since the older types used a local battery to run the carbon microphone; that's what the lower compartment of a wooden wall phone is for). There are other sources, some very authentic with a little effort but the more, the better.
Another old clock you might remember is the Telechron. These wall clocks, in 10" and larger sizes, usually have a small dot about midway between the center and 12 that goes red for 12 hours and white the next, to mark p.m. and a.m. The little 60-cycle synchronous motor uses a sealed rotor and it takes serious skill to open one up and get it running again. And, yes, there's a fellow who does just that, at TelechronClock.com. (I wonder if he would tackle the noisy motor unit from my Numechron Tymeter mechanical digital clock?)
* A misnomer, since they consist of a single, large dry Leclanché cell. A battery would be more than one. The irony is, modern #6 "cells" contain 2 or more F or D cells in parallel: they really are batteries.