These plates are not cast at Derby and were cast at St.Rollox. The LMS letters and whole plate style are St Rollox through and through. These are replacement plates that seem to have been fitted as a replacement for the normal Crewe type when passing through the works (heaven knows why?), they occur infrequently and are easily identifiable by the spindly and badly defined Derby letters.
Often mistaken for brass these are cast in Bronze and as such have little in the way of patina on the rear. They are rough cast and badly finished in general.
Basic dimensions in inches- touch 10 & 7/16ths by 5 & 7/8ths, 1/4 thick, holes 8 & 3/4 std.
Pattern Rarity- Not Common
Special Features- Top right of plate has a bulge / flat spot on inside of rim common to all St Rollox replacement plates, also impression left by spikes used for lifting pattern out of mould are inboard of the mounting holes or a dint where those spike holes have been filled or closed with the moulders finger.