world's thinnest watch|thinnest smartwatch in the world EMD: F7. The Reading's final diesel freight cab units were the 24 F7 locomotives in class DF-4. The class was split between 6 locomotives coupled as A-B units numbered 266 A/B to 271 A/B, and an additional 12 A units numbered 272A through 283A. The F7s were one of EMD's most popular locomotives, with over 3600 units being constructed for most . Subscribe