Noice. Sight rails were first used by Berns-Martin, in the late 1930s, on their Range holster for carrying bullseye shooters' target sighted 1911s; and popularised beginning around 1970 when target sights had become de rigeur in the leatherslaps of the '60s. Here's theirs, in their Raider that followed the Range holster in the late '60s:

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Red Nichols The Holstorian