Hello, this has been discussed in the past and there are probably some very good threads if you did a search for holster care. On your left at
www.lugerforum.com is an article on Holster Care and Preservation.
Overall consensus is that putting nothing on a collector holster is best.
I have used Pecards and found it made the leather look much better, but several experts have stated that putting any kind or "preservative" can have the opposite effect in the long run.