This is a pretty obscure build even by my standards, I made this based on an original design by Ian Scoones for the teleport bracelet for series 1 of Blake's 7 at about the same time I made the other bracelets, just never got around to doing a pic of it until now, for quickness I just replaced the actual series 1 teleport from my older picture with this one. See Labels below.
The concept drawing this was based on was in the book Blake's 7: The Inside Story published in 1997.
The description gives the measurements as Length - 5-½, Width 2-½ and Height as 4 inches. Which makes for a pretty chunky bracelet, no wonder they went for the slimmer ones in the end. He notes it should have a white plasticard finish with foam rubber around the wrist and that 30 of these be made with 6 extra breakable ones.