While going through some miscellaneous bits and bobs acquired over the last 50 years or so I can across an Irving Focuser. It was on an f/8 8″ Newtonian I bought second hand in 1985 (it may have been Fullerscopes – the mount was a MKIV – but I’m not sure about the tube).
Its a rack and pinion with a brass thread where the eyepiece goes. The tube itself seems to be steel. The paint job is a bit scraped, but it works well enough. Doesnt look ancient. 1960s perhaps.
Anyone who wants it is welcome to it for the price of postage/Hermes to you.