Really old water heater?

I came across this water heater in an attic in a house supposedly built in 1980.

It’s a Rheem, and in pretty sad shape, although it still produces hot water. All the info I can find says it’s made in Nov 1975.

Does anyone else have any info that would say otherwise?

Randy

http://www.buildingcenter.org/

Thanks, John, that’s one of the places I got the info from.