Are you wanting to know based on look, feel, or the info provided?
Visually if you’re buying online, it’s virtually impossible from pictures. Even in person it’s difficult because on finished products, the edges are usually hidden, as is the back because of linings. On a brand new product even an expert would have trouble.
Now if you’re in person, you should have a better idea by feel. Anything too rubbery or plastic feeling is a red flag.
Brand, reputation, country of manufacture, and price will also tell you a lot.
If the maker tells you where the leather comes from, that’s a good sign. More specific is better: country is good, the tannery is better, the exact tannage is best. Examples:
One thing that helped me find my way was just going out and interacting with quality leather products at high end stores and getting a feel for quality, then finding common denominator descriptors for the items that I liked most. I think leather can be really subjective and there’s not one variety that every individual ephod love to wear, but for example I found that my favorite leather jackets were largely lambskin. It might be best to jump in and do some tactile research rather than trying a trial and error approach with your hard earned money.