Your cell is a handsome find, Dave. Thinking out loud—don't think a zinc-plated bolt would give much life, and the iron might contaminate the electrolyte, but maybe that's not the point. When you see a jar one thinks of a flooded lead/sulfuric-acid cell. That would not work here for the acid would dissolve the zinc electrode without any current flow.
The old No.6 1½-volt “dry cell” used a paste electrolyte—may have been partially zinc chloride. In those, underneath a cardboard wrapper was a cylindrical zinc cup about 2½ inches diameter and 6 inches high. There was a 6-32 knurled-brass nut attached to the zinc that was the negative electrical connection [cathode.] The positive/anode connection emerged from the cell top-center with a similar brass nut. The anode was a carbon rod about ¾-inch in diameter; maybe 5½ inches long.
Believe it or not, there is reference to No.6 cells in the 1999 NEC...725-41(a)(5). Have to see if I can find more information about just how your cell is filled/operated, Dave. For you young’uns, the modern equivalent to No.6 cells are Eveready EN-6. They are advertised at ~$11-to-19 each. http://data.energizer.com/datasheets/library/primary/alkaline/energizer/industrial/e n6.pdf
[This message has been edited by Bjarney (edited 09-10-2002).]