What is this

I recall seeing a similar-looking device in a recent post, also asking "what's this". I recall that was a later car ~1975+ so may not apply. I also don't recall the answer. I think 1972 was too early for the seat-belt ignition interlock relay (under seat anyway I think). Your hot-water diverter valve near there should be vacuum-operated. The horn relay looks similar, but usually on the driver's side. Might have to do with the heated choke system.