G'day Barry. I can indeed confirm that the phenomena you describe is very common with vintage blades. There are many theories on this matter, and I have put some time and analysis into the issue, including laboratory analysis and observation (a perk of my profession). My conclusion is that it is not due to micro-corrosion of the blade edge, but a build-up/deterioration of the synthetic coating and/or other detritus that has accumulated on the blade edge over time. It sloughs away after the first shave, and the quality of the shave usually improves. To mitigate this issue, I lightly strop a new blade a few times on a hard rubber mat lubricated with lather.
Regarding the blades, the Super Stainless blades were prominent in the mid-late '60s, and came in several variants. The were succeeded by the renounced "Spoiler" in around '74 as far as I can ascertain. A personal favourite of mine in the Super Stainless range is the "Aussie Spoiler", made in my home country of Australia. All the blades listed are excellent performers.
Here are some examples:-