??? - original exhaust headers - anyway to ID?

just curious on the pedigree of my 74 Mk2 - question - anyway to ID original exhaust header pipes. on one of my previous posts on mufflers, the issue of weld quality came up. I was cleaning up the exhaust, so here's a couple pics of my header pipes - one on the weld quality, and one shows the letter "D" stamped near the pipe's exit flange. any guess - original, aftermarkets, or replacement pipes? TIA -