The 5687WB is a special quality double triode. It is described as a general purpose medium gain triode pair with good emission. The pair can dissipate 7.5 Watts or a single triode can dissipate 4.2 Watts.
The W suffix denotes the special quality build and the B suffix indicates a third version with slight improvements. The 5687WA would be a SQ version with slight improvements that preceded the B version.
The top mica is thick to resist the effects of vibration and the anode fixings are diamond shape to offer good grip to the mica.
The two halves of the anode meet at the centre of the working face and the flanges form the fixings and are stitched together. The grid wire is just visible and passes flat across the cathode.
The anode with the copper grid supports visible above and below the supporting mica sheets.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 45 mm tall.
