By far the largest non-passenger class of vehicle owned by the railway the "M" series wagons were abundant across the network but remarkably were largely scrapped in by the 1960s, only one remaining into the 1980s, being in a very poor condition.  In additon to the I.M.R. wagons, a series were also inherited and re-numbered with "r" prefix from the Manx Northern Railway as below.  Please note that were scrapped dates are missing this is purely because they are unknown, as all vehicles bar the "new" M.78 no longer exist.

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.The wagons were painted in a uniform mid-grey livery with white lettering denoting fleet number, originally with black shadowing.  There was one "Double M" (or sometimes "MM" class made from a bogie underframe, see separate entry for this vehicle.  Today, the sole remaining wagon M.78 is in use and this vehicle was completely rebuilt by the mainland based area group of the Supporters' Association.