Finding vintage blades can be fun, I look for deep pits and curves in the blade. A little surface rust is not bad, as long as it is not near the cutting surface. I have purchase a ton of ebay blades 50 percent success rate on them half are complete junk, every once in a while a diamond in the rough shows up.

My advice go to the classified, or buy a NOS from a vendor here. You may want to try a razor complete different from what you have, bigger or small blade, different point, different material SS or Carbon. This is the time to see what you really like

Crom