Region's fleet of electric multiple units, saw classes being allocated according to the following division: 40x: Southern Railway designed units 41x: 1951-type British Railways designed units 42x: 1957-type British Railways designed units 43x: 1963-type British Railways designed units 44x: 1967-type British Railways designed units 45x: Underground ('Tube'-sized) units 46x: 1971-type British Railways designed units In comparison with the later re-arrangement, it is worth noting that types that were different were given the same class (e.g. the single-car luggage vans) and identified only by subclass, while those that were later treated as variations of the same class, were separated according to their construction period (e.g. early or late 1950s builds). When the new arrangement was applied, 40x classes were left untouched, but the others were changed as follows: References British Rail numbering and classification systems