Most of the Ruger flapholsters were made by Bianchi and say Bianchi on the, something like 170,000 in all, only about 10% of which were left hand. Bianchi holstes were offered in 16 different models (eight in right and eight in left, including the Old Army)
Then there was another company by the name of Cathey who produced about 10,000 flapholsters for Ruger about mid way through the Bianchi production. I don't think Cathey produced all 16 different models though. The Cathey holsters are identified by a large Ruger eagle logo on the belt loop, and the Cathey name does not appear.
Overall, the rarest of the flapholsters are for the Old Army, and especially in Left hand.
Chet15