That's about what I was thinking-providing there is a galvanized coating under the yellow polyurethane coating. One chance a buyer would be taking is the inside might also have a coating and I'm not too fond of that.Unfortunately the tank is only worth what someone is prepared to pay you for it. There is no market per se. I’m guessing $40-$60 but you may find someone who absolutely has to have it - even better when two people want it. Personally I’ve dumped more than I’ve kept of that vintage.
@simonbeans might be interested in the back pack.
The most value the OP will get out of the tank is to have it inspected, re-certified, and dive it. For regular single tank dives-especially shore dives-the good old 72 is still my favorite.