The main difference between winter and summer is the summer hide will have sparcer hair, It will be longer and in some cases even finer.
There will less under fur (winter hides have much under fluff)
The pelt it self will feel lite.
The hair on some hides will be light in color with sun faded spots and bare areas.
Looking at the under side or tanned side many times you will see new hair of what seems to little stubes .
Better yet just ask.