Master cylinder is back together and appears to be functioning well.
Cylinder polished to 2000 grit, all moving parts inspected and edges polished.
I got a kit from GT Car Parts which they sell for this application, but I think it must be a sort of multiple application kit because in addition to having a lot of bits that weren't needed the kit only came with three of the rubber "doughnut" seals whereas my master takes four. We went ahead and used the three new ones and reused one of the old as the old ones looked to be in excellent condition and we only ordered the kit as a precaution.
Just as a heads up, I also checked with Rutlands and the suggested a rebuild kit that was clearly for a master with a 7/8 bore.
SII perhaps? Definitely not SI.