This first five photos (NRM ref containing DY) illustrate various stages of the construction and assembly of railway carriages at Derby Carriage Works in Midland Railway days, prior to the formation of the LMS. The remaining photos (NRM ref containing W or WOL) show various stages of the construction and assembly of railway carriages at the ex-LNWR Wolverton Carriage Works in LMS days.
I hope this serves as a useful introduction to this valuable resource, and await with anticipation for the NRM to publish further photos from their archives.