Appears to be a '67-'69 Firestone 70 series tire that was labeled "SUPER SPORTS" and was nylon cord construction. These were the tires that had 20K tread life under "normal" conditions.
Easy to read date codes were not used until Firestone implemented DOT standardization during the '71 model year. Where your tire is labeled ...6SR, the 6S would be the 2 digit week number, and the R would be the last digit of the year, if the tire were '71 or later. This photo is a similar pre-'71 tire without a date code.
I managed to ruin 4 of these in a couple of hours by driving 90 mph on a hot day in Wyoming which had no speed limit on highways back then. The centers wore out from over inflation due to heat caused by speed.
Meguiars tire shine aerosol spray and similar products has done a good job of masking chemicals leaching out of old tires. Try a small spot and see. Minor abrasion might help.
