This plate simply bears the legend of LMS REBUILT DERBY as previously explained for the non year BUILT plate, I believe that given the decision to backdate so many locomotives of Midland origin the decision was taken to simply re-brand rather than altering the year on the rebuilt pattern for the vast majority of locomotives. That said it is notable that many Rebuild plates exist with a year on, particularly 1920 and 1921 or other years during which mass rebuilds of 4-4-0 types is undertaken so long runs of the same year plates would be possible.) But as I have said before imagine trying to replate the multitude of engines Rebuilt or Boiler New (another way of saying Rebuilt) within say the the MR 2F and small freight classes! Again the LMS did not need the data on the plate as rebuilding data was stored on the engine record card. As for the Built version, I believe this to be a totally new pattern on the LMS made at the same time as the Rebuilt plate with year, there is some size variation of this pattern pointing to two patterns.
Size in inches- Typically 10 & 3/8ths by 5 & 15/16ths tho examples at 10 & 1/4 by 5 & 7/8ths. (hole centres 8 & 3/4 typical)
Pattern Rarity- Common