This is Sylvania 702AT/R switch vacuum tube. It is dated November 1944 and listed as U.S Army Signal Corp stock. I have not been able to find much about this specific tube other than it seems to have been used in the transmitter sections of WWII era radars. It appears this was the first TR switch that was intended to be ran with a magnetron transmitter (from what I can tell this was invented in 1941). This tube would switch an antenna or transducer to either a transmitter or receiver. This was commonly used on the BC-640A WWII transmitters.

Essentially it is a single double throw switch, the center disk with the two poles is the common which is switched to either of the other disks.

If you have any more information or a corrections please leave a comment, would love to know more about this one!

Sources:

https://www.radiomuseum.org/tubes/tube_709a.html