Personna GEM blades are the ideal companion for your GEM razor and also some other models of vintage razors. The blades are made from stainless steel and coated in PTFE. The blades are quite a bit thicker than double edged blades most of us are used to (0.23mm vs 0.1mm), so expect a few more shaves from them before the go dull.
The blades has an alumium back that can be removed should your specific application require this. Blades are individually wrapped with cardboard to make sure they stay nice and sharp before getting put to use in your razor.