
This is an ASTM "TANK", manufactured by Manchester Tank
https://www.campervan-hq.com/products/rv-propane-tank-9-8-gallon-manchester-model-6840?variant=29572867975&network=g&device=c&keyword=&campaign=10753893734&adgroup=pla-932594732562&gclid=CjwKCAiA866PBhAYEiwANkIneHaO__XhPEEqm7XBg0GlQUFOE7DXKVbBS_MjXcD75TdIclZH5lvMkBoCwnsQAvD_BwEFrom "camper van hq"
I don't know where this company is located but they sell them and could probably give you good advice on where to go next.
I may be possible to salvage your tank by removing all the fittings, and sand blasting or glass bead blasting the paint and rust off. You can clean it (inside and out), paint it, and replace all the various fittings. 4 new bolts and nuts, along with washers, and you are back in business.