[OG68]

I see them all the time on Ebay. Sometimes their listed as 68-72 or as 69-72. I think, and I'm sure Scott will verify, that there are three different versions.
I don't know what year, if any, had the numeral 6 added

I bought my 68 clock as a parts only. It was advertised as a 69 and was in pieces. I figured for $30 what could go wrong.
The contacts weren't burned and I gently cleaned the mechanism and lubed it up. Hooked it up to a battery and it ran for several days. Bought a new lens and now have a very nice clock.

BTW the dog hair at the 8 o'clock position has been removed lol.