In my experiences repairing vintage test and telecom equipment I’ve into issues with dried out leather/rubber items, mainly belts, idlers, handles and straps. A really simple and inexpensive way to restore most all of these leathers involves cleaning with saddle soap to remove any surface dirt/oils and a few applications of conditioner to restore the moisture.
I have been really surprised at how much this works..
Here is what I used:
Please take care of each other.