I don't think this would be compatible with Schuko sockets because the plug would need two notches to accommodate the Schuko ground pins and the lateral guides

I don't think this would be compatible with Schuko sockets because the plug would need two notches to accommodate the Schuko ground pins and the lateral guides in the socket. It's just regular old type-C to me, I have some very similar plugs (in bakelite indeed) lying around from old French and Belgian appliances (ironically, dating from a time where power in France was 110V).