Jack Alexander has let me know that there were two others involved involved in the design of the Miltra range as well as Bish and himself, Barry Warby of MMS and the late Lyn Heywood.
The following three posts comprise a series of articles in Miniature Warfare from 1971 by Bish Iwaszko. A leading light of the London Wargames Section, he was the author of their Modern Rules (essentially late WW11 and post war). These were notable for using a logarithmic ground scale (no, I have no idea what this means either).
Bish Iwaszko is on a par with John Sandars for the quality of his modelling, particularly when you realise what was available in the early 1970s. These articles are profusely illustrated with photos of all kinds of intersting kit and give an idea of the quality of his work. They do however seem to stop a bit abruptly: I have checked later issues of the magazine but this seems to be where it finishes.
Iwaszko was also the proprietor of Miltra, a military training aids company, which produced a range of 1/72 figures, originally for museums, then made available to wargamers and modellers at the end of the 1970s. These were popular with modellers and dioramists as they were mainly in relaxed poses, and were customisable with separate weapons and equipment.
I have posted some information on the Miltra figures ranges over onThe Old Metal Detector.