Capt Jas is right - up to a point - there is shene and then there is "shene" - one is the shene of newness and the other is of well cared for use. It really depends on the type and make of leather and one's mental image.
With all due respect to Steve L (a major cratsman and a wonderful gent with whom I have thad the pleasure to discuss our mutual passion) - by type and make I mean: is it a bark tanned leather pouch made by a commercial maker? an Indian made one of brain tan? or a rough pouch cobbled together by a frontiersman out of left overs or his own alum tanned? on each of these the finish is going to be different based on the materials/make, but also on whether the finish one seeks is new or used (example: a brain tan pouch in new condition would have no or very little shene, the same piece aged would pick up a shene due to handling, oil, blood, etc., but used it would also have bare "rub" spots - you'll not on the one pictured above that there are both - the wear/shene/age was all based on pieces with "real" wear and tear.........more complications, but IMO all must be considered when building "period" gear - after looking at several thousand pieces of original leather over the last 40+ years, from medieval to early 20th century, I can only say for me there are no hard and fast general rules - it all depends on what the "base idea" your working from is..........