He didn't wear a 'Half-Breed' rig - more of an 1890's skirtless style with a money belt - or even what El Paso Saddlery calls the '1930 Austin'.
His costuming came from his personal wants and desires - not from the pages of history - so don't mistake the 'John Ford Reference Library' for an actual reference.
The 'Half-Breed' holster was a spring-retained shoulder holster and not that leather cartoon worn in 'Tombstone', either.
It was worn vertically - under the armpit and with a cross-chest retaining strap - the spring holding the cylinder, with a cupped toe containing the muzzle.
If you want to know what was actually worn and when, get a copy of 'Packing Iron', by Rattenbury - it's what has turned into the model for modern holster makers replicating the era.
Scouts Out!