Thanks for all the interest and assistance folks. We shall get there in the end. I have e-mailed Natalie Braber as suggested by LFF but no reply yet. Have also e-mailed the company Arthur Dudley in the Black country. Again, no response yet. However I'll hang on in hope and expectation.
This very day, I have decided to have an excursion to the National Mining Museum near Wakefield. Its something I have been meaning to do for ages but never got round to. I may be able to glean some information from them, maybe before they reply to Ray Padgett.