Until about the year 2000, Ruger black anodized the alloy parts. For a proper restoration, that's the only finish that will replicate the factory "look". You may find a metal finisher in your area that does this.
Since 2000 Ruger uses a black Powder Coating which is a baked on finish. I think it looks better than anodizing but it's not correct for an Old Model.
Many places do Powder Coating.
The best and most durable do-it-yourself finish is a spray on that must be baked. Ceramikote is one. Brownells is a good source for some of these.
Any of the spray on coatings that do not require baking are a waste of time and money. Unless you never use the gun, they rub off in no time.
My number one choice is a take-off blue steel grip frame to replace the alloy frame; the alloy ejector rod housing too.
