Only just come by this discussion on LNWR and MR going to the LNER (M&GN). The former Midland clerestories were were to MR D598 lot 752 50ft 3-compartment corridor thirds with an open saloon at one end. Some were merely re-lettered M&GN while others were given a brush over with LNER brown paint before being re lettered. Example numbers were 99 and 81012. They used to be available as etched zink sides from Trevor Charlton.
Twelve of these semi-open saloons were transferred to the M&GN in March 1936. Later they were given LNER numbers and "livery" although still lettered M&GN. Some lasted until 1955 having by then acquired new numbers alloted by BR.
Derek L. and I built & painted quite a few of these coaches (4mm) from Charlton parts in the 1980's, mostly in full panelled LMS livery with M&GN insignia, and a very few in LNE brown livery.
Going off my old pencil written notes, Nos .99 and 95 were electrically lit, while No. 99 was destroyed by enemy action in 1945.
Hope this is of use.
Larry G.