I'm not 100% from the single photo that it is the sand resistor, on my similar era Bally it broke down to a single wire with evidence of the sand/cement block remaining at each end, more photos from different angles including what it's connected to would help. They were used on several machines wired in series to the Tilt (or sometimes labelled Hold) Relay, something like 15 Ohm / 5W easily available from ebay etc. Which Relay is it wired to?
As mentioned in my first post, do you have the schematic? the resistor would appear similar to the snippet below, if not search the schematic down (e.g.
http://www.pbresource.com/mansch.htmlyou'll) you'll need it over time believe me
If this guesswork is correct then it's part of the tilt circuit which is basic on these games you could live without it in the meantime.
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