They are the back pack frames for the A-13 which was a British HF man-pack transceiver.
I have several frames and severals sets of the radios, still needing some parts to completed them. Mine came back from Singapore when 1 RNZIR came home to New Zealand. I have only ever seen one complete set. I 'll try and scan a photo in tonight. The reason for the several styles of back pack is that they were a modular radio and had Transmitter units , receiver units, Battery Charger, Hand Crank Bat charger and from memory depending on how and what you built will depend on what pack you will need. I will try and get some more info from the manual when I get home.
regards
kev
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