[Milsurplus] Mystery transmitting filters CU-731/SRT and CU-732/SRT

[Nick England]

Here is an interesting gadget that I can't figure out an application for.
http://www.navy-radio.com/xmtr-tuner.htm#cu731

HF Transmitting high-pass and low-pass filters
but 180 ohms, 50 watts power limit, and single wire connectors??
How would such a thing have been used????

Any suggestions???
Nick K4NYW
www.navy-radio.com