The minute I saw this threads title I thought "xSF med has a lot of experience with old leather. I wonder he will share with us his brand of night cream".
and I thought... Mac has a lot of experience rubbing one off, he should be able to give lots of advice....:)
Actually, a good leather conditioner - Lexol, Mothers and Guardian make good products - the key to bringing back leather that has a low moisture content is getting the oils back into the leather.
Remember - Saddle soap only removes surface dirt - it will dry the leather - due to the age of the holster, a very lightly dampened cloth for the saddle soap and allow to dry fully prior to using the conditioner.
When using the conditioner, the color of the leather may change (darken slightly due to the re-absorbtion of oils) - makes sure all surfaces - even way down inside the gun pocket and all edges get a t least 2 -3 good coats of the product - allow acoupe of days between applications, and buff with a soft cloth between applications.
Neutral shoe polish (Kiwi, Guardsman, Lincoln or Meltonian) as the final protective coat on the exterior of the holster - probably not all the way down into the gun pocket since it can't be buffed out all the way and might get into the slide rails of the "shoot'n ahrn".
As a second thought - if you were to render one of the kiwis from this board, you could get all of the oil you needed to condition the holster... but then the holster would be unintelligible and have a bad attitude.