Anyone recognise these ???

[GM1BSG]

Attached are three pictures of what look to be some kind of power devices by Eimac.

I did a bit web searching but as the numbers also correspond to some telephone numbers for valve dudes google is a bit tough going.

If anyone recognises these, please reply.

John

[MM0BSM]

The Y-540 is a rugged planar triode designed for switch tube or pulsed regulator service in advanced groun, airborne, or space applications.
Design features include an arc-resistant cathode to assure stable and reliable long-life operation under adverse conditions. An added feature is the increased grid-to-cathode insulator length to permit operation at high plate voltages and/or higher altitudes.
The Y-540 is normally supplied without a radiator and may be conduction, convection, heat-sink, or liquid cooled, as immersion cooling in an insulating medium (e.g., FC-75). The tube has solder tabs on the cathode, heater, and grid terminals.
Specifications:
Amplification Factor (µ): 75.0 (145 Mu)
Cathode: Oxide-coated Unipotential
Anode Current (A) Maximum: 5.0
Anode Dissipation (W) Maximum: 150
Anode Voltage (kV) Maximum: 8
Grid Dissipation (max.): 1.5 watts
Plate Dissipation (max.): Depends on cooling technique
Anode: Threaded stud, 5/16-24 UNF-2A for heat transfer and electrical contact.