This is a good topic Gary. I am a big fan of natural leather that has had a suntan and some oil. I think you will find natural leather was much used.
One big mistake I used to make though was to oil my leather prior to burnishing (actually I was doing little at burnishing at that time) and I was critiqued on that by Steve Lalioff back in the early nineties.
I have found as a general rule that a quality leather will usually take a tan and a burnish equally well. Add to that a light oiling and its a good look.
The flap on this pouch started out baby bottom pink and has just been wrinkled, suntanned and hard burnished with a little moisture present.
This before and after model is a good one.
As soon as I can get my pc back online I want to post some pics of my last pouch at a very light aging stage compared with the way it was delivered as ordered.