card case 
Article used to hold, organize and protect identity papers and other cards while making them easily visible.
slot 
Narrow elongated opening into which a card is inserted with a part of it projecting so it can be easily recognized.
ID window 
A window behind which an identity cards is inserted to protect it and make its front side visible.
tab 
Small piece with a fastening system that extends a flap or goes over an article’s opening to fasten it.
bill compartment 
Flat compartment between the back and the inside of a wallet or a card case where banknotes are kept.