The M.C.M Wedge came with a box of photographic bits and pieces from the auction site. It consists of graduated grey strips of cellulose graded from 1 (clear ) to 9 (black) sandwiched between two 4 inch glass plates. It has a satin lined fitted case labelled M.C.M Wedge Manufactured by Ilford Limited. I wondered what it was for and was surprised to find a Google hit to the excellent Photomemorabilia website, with a PDF of Ilford News for Photographic Societies, Series 1 Number 5 of March 1939. LINK --- https://www.photomemorabilia.co.uk/Ilford/Chronology/Ilford_News_Sr1No5_Mar39.pdf It says "The M.C.M. Step Wedge has been designed by the editor of the Miniature Camera Magazine in collaboration with our Research Department as an aid to serious photographers who wish to classify papers by an accurate method of testing." But, tantalisingly, "It is impossible to give full details here owing to space limitations, but readers will find a full description in the Miniature Camera Magazine for March." So - any ideas?