Custom period counter
The counter decades are incomplete, missing two tubes each. The type of tubes is unknown, but HP used counters like this in the early 60s and their decades are probably identical. There are another 11 tubes on the chassis, probably the pulse forming circuitry for the triggering signals (external). There is no timebase in this counter. This instrument may be able to count pulses to somewhere between 1 and 10 MHz. There are no markings for line voltage or manufacturer. With tubes missing it will certainly not work. With tubes replaced it may well work although the condition of the existing tubes is unknown.