The single item of its type, in the center of the first photo, is a Number 19 Wireless Set mount for a Variometer. The rings with six holes are usually made of wood but I've heard there was also a rubber pattern. It is used as an insulator for the cone shaped aerial mount which is used for the Number 19 Wireless A-Set. The B-Set aerial mount is usually about 4" tall and 1.5" diameter rubber and the aerial itself is about 2.5' long being for short range formation transmissions. The rubber part would mount onto a short pipe looking thing. Don't you just love technical jargon
Looks like the short and long straps are the lengths used for power supply and transceiver to each fasten down to the mounting plates when side by side. The middle size strap used for the PS/U to attach to the top of the transceiver has thus far also eluded me. I built one following a tip from another forum member, by lengthening a spare short strap. So there are at least three of us needing the medium size for our wireless sets.