Gas tank restoration

[R68GTO]

Tank straps are painted black, not sure if 30 or 60% gloss. Photo of my strap below, original black paint evident where the strap was tight to the tank.
As far as the steel manufacturer's mark on the tank. Those are stencils that were applied to the strip after it was cold rolled to the final gauge at the mill. I do not know if there was a required or standard spacing of that stencil when it was applied, but there would have definitely been a space between stencils. If the spacing was close enough, you could potentially have it appear on every tank made from the steel coil shipped to the tank manufacturer, but you can be fairly sure it would not "land" in the same place on every tank.
Our business slits millions of tons of steel every year for all the domestic steel mills and apply stencils to some of that metal. These days the stencil requirements are everything from continuous through the entire coil to just marking different areas of the coil. The requirements are generally driven by traceability for quality purposes.