Friend dropped in.....

[Sapper740]

How about "this one" seen on eBay UK, chaps? I'm not quite sure why anyone thinks the silver paint may make it Parachute Regiment?

I would have thought that this example is a surplus spare valve case repurposed for another use.

WWII British Army Parachute Reg Wireless Set No 22 - Z.A 14041 Spare Valves Set for sale | eBay

The WS No. 22 along with the WS No. 38 were carried by paratroopers in WWII although I wouldn't want to have been the wireless operator stuck with humping the 22 set which weighed 36.5 lbs.! What is for sale in your picture appears to be a home made step down transformer and filter to produce rippled D.C. and is not military. The 22 Set was a scaled down 19 Set with no provision for intravehicular intercom or long range voice communications.