think what you have is a 1935 chev master tail light pot , also fits a 1936 master and standard. It looks like the little L shaped bracket across the rear has been removed.
The back of the tail light pot is the key. Fender mounting arms 1933 master and standard---1934 master and standard--1935 standard are different than the back of the 35-36 tail light pot
The lenses are aftermarket, originals have the name CHEVROLET cast into them.
The red lens and the metal retainer are all the same 1933--1936 Just the pots differ. Your missing the metal retainer clips on the insides of the pots that hold it on
mike