The best sure fire ID is to hook up a known positive voltage to the end with the band, and see if it blocks the positive voltage. Then, reverse the supply to check for forward conduction. An ohm meter with known polarity can do this on X100 scale, or on modern DMM ones, they have a diode test scale that will read 600 mv when you have positive voltage on the opposite side to the cathode. 73, Stuart K5KVH