For leather holsters, always be sure that you are purchasing items made with vegetable-tanned leather. There are other tanning methods, and many leathers (including nearly all suedes) are chrome-tanned, a process that utilizes chemical salts that remain in the finished leather. Moisture and heat can, and frequently does, cause surface corrosion to carbon steel, nickle-plated steel, and even stainless steel.
Never store a handgun in a leather holster or case. All leather items will attract and retain moisture. Get into the habit of removing your sidearm at the end of each day, wipe it down, and store it separately from the holster. Store holsters in an area having good airflow so that residual moisture can evaporate naturally. Don't try to force evaporation with excessive application of heat.
That said, your Model 60 is made of a stainless steel that is pretty resistant to most environmental issues. A vegetable-tanned leather holster made rough side out/smooth side in will probably be as good for protecting the finish from excessive wear as anything. The rough side out also provides good friction inside the pocket, allowing the revolver to be drawn easily without the holster coming out with it.