The more you can narrow your question, someone can provide a better suited answer.
Sorry if this seems way off what your after, but what your asking is like saying is there a way to tell if a car is good quality, without saying anything else. Theres such variables from Manufacturer then New High End right through to second hand, drive em till they clap out. Any can be good quality depending on your needs.
Quality can be different things,
If your re using leather from a old item and repurposing it, or have been given off cuts then quality comes down to how suitable it is for purpose intended, in the same way quality can be down to parts of hide & the cuts purchased, which are used for specific projects, a good example would be belts, you could make a belt from any leather.
HOWEVER its quality is shown by what part of hide the belt was made from. Quality Belts wont be made using leather from the belly, its floppy, loose grained and will stretch easily, obviously this would be a poor choice for its intended purpose.
Quality is very subjective, if like me (I am a hobbyist) I purchase leather "if & when" I see it, at reasonable (to me & my budget) prices, from a shop near me, that happens to get it in occasionally.
In my situation, is this leather Im looking to buy, good quality or in good condition... ie. "usable for what I want & looks good"
If its Veg Tan leather, your nose will tell you if its got a mild or strong "leather smell" or if its smell has a"old dusty leather less" smell, this may hint at its age combined with its suppleness... (has it been in storage for ever and just re discovered) I look to see if its supple and flexible and its not "board stiff" dry or starts showing it would crack or split as I bend/fold its edge (bare in mind you may need to wet leather to bend/fold it fully) if its pre finnished it will be stiffer than natural finnished (skin coloured).
Leather being a natural product can have scars even holes, the less scars the better it is graded, I believe.
On the other end of the scale, buying from a supplier.. have they sent you a quality hide for what you paid verses what you expected.