1990-1991 NAS Millington.
Would you happen to remember the Plate Voltages on these 1000P 4 tubers?
I can't swear to it but 790 VDC seems to ring a bell.
I went through Glakes "E" branch in 1974. They told us that tubes were not going to be included in the curriculum in the up coming classes after April 5, 1974. I guess the fleet got tired of replacing Simpson 260's and the PSM4 meters. Those meters took their toll on transistors as well with the low input impedance.