Scarcest in series. 2" brass frame has large raised aluminum knob at center and pair of small cut-outs through which either a number or letter shows. This is the scarcest of the decoders as the reverse is a dark red plastic insert held only by means of two small internal tabs so the decoder back was easily lost. Center of the back includes glossy silver luster rectangle of metal to be used for signaling purposes. Front of the piece has bright, near complete luster. Case back fits snuggly. Exc.