this method of classification was that it did not distinguish between particular classes of locomotive, so many very different types would have been classified '4F' for instance. The tables below provide definitions for the numbers and letters used: F : Freight (from 1928) G : Goods (until 1928) MT: Mixed Traffic (Freight & Passenger) P : Passenger XP: Enhanced Passenger (higher end of power range) A single number without a suffix letter was originally used by the LMS on locomotives that were not of Midland Railway origin until 1928. Thereafter, it was used to indicate a mixed traffic locomotive. Where a mixed traffic locomotive fell into different power ranges, dual classification was used, e.g. 5P4F. From 1953 until 1957 (but remaining painted on locomotives until much later), the suffixes 'FA' and 'FB' were sometimes used to distinguish between freight locos with different load limits due to their braking characteristics on unfitted goods trains. London, Midland and Scottish Railway Locomotive classification systems