The EM87 tuning indicator uses the closing bar principle and is housed in a standard miniature valve envelope. This exhibit carries no makers name.
This valve has the same base connections as the EM85E and differs in sensitivity, anode voltage and anode current. The manufacturers short form catalogue lists both as tuning indicators and gives no guide as to differences. The base connections are also the same for the popular EM84, although the EM84 has a much greater voltage range.
The electrodes are mounted horizontally with the amplifier triode closest to the glass envelope.
The side mica with the heater/cathode on the left.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 66 mm tall.
References: Data-sheet & 1040. Type EM87 was first introduced in 1961.