in about 1970 the fleet was renumbered into a common Region-wide series and from about 1972 permanent set numbers began to be painted (or applied by transfers) onto the ends of units, beneath the right-hand driver's cab window (as viewed looking directly at the front of the unit). Network SouthEast NSE adopted the former Western Region series, and expanded it to include diesel multiple units used on the former London Midland Region, which took unit numbers in the 7xx series. This included units from classes 101, 104, 108 and 117. Regional Railways Sprinter (Class 15x) units carried the last three digits of their carriage numbers in the 52xxx and 57xxx series. The 6xx series was reserved for the aborted Class 157, and was adopted by refurbished Class 143 601-625 and 101 651-695. Refurbished class 117 and 122 kept their Tyseley 3xx and Laira (Western Region) 1xx unit numbers respectively. Electric Multiple Units Eastern Region When introduced, Class 306 were numbered 01-92 and Class 307 01s-32s. These numbers were amended as they were converted from 1500 V DC to 25 kV AC operation. Parcels and departmental units in the 99x series have included Classes 308/4, 302/9, 316 and 937. London Midland Region Scottish Region British Rail numbering and classification systems British Rail rolling stock