I've seen some of the "blue" jobs done on the receivers of post '64 M94's. Sometimes, they come out purple. It's not very attractive. I don't know how electroless nickel plating works on these receivers, but if you don't like the idea of chrome, you probably wouldn't like the nickel either. The Robar finish would be pretty durable, but it wouldn't duplicate the factory blue by a long shot. I saw a tip in Brownell's "Gunsmith Kinks", volume 1 about this. One gunsmith says they're cast iron receivers, and never polish up very smooth before blueing. Another says he leaves them in the blueing tank for 2hrs, and has to cool them gradually. They still come out purple sometimes. There have been people do this work on these M94's, but I haven't seen a good one yet. Best bet would be to contact USRAC to see if they can re-blue, or leave it "as is", character intact.