MY late 69 SCJ had the original tank (look like this) !
I used OOOO steel wool and phosphate to clean
ALmost positive that there is a date stamp on the seam - I"ll bet Marcus will see this and WILL BE A TOPIC !! LOL
THere are not many that know the USS run numbers on there cars as the stamp MAY or MAY NOT be on 100% Mine wasn't all there but nes 69 7236 was.
Mark
P.S. Phosphate removes ink !