They were in effect a continuation of the 645 Class, with longer frames though using the same 4'6" wheels and 15'6" wheelbase, and they were the last of the larger type of tank engine to be built at Wolverhampton. Pannier tanks were later fitted to all of them, apart from No. 1772, between 1912 and 1930. They were nearly all Northern Division engines until the 1920s, though later Weymouth had as many as five. Withdrawal started in 1928, but 21 continued into British Railways ownership. Nos. 1782 and 2719 survived until November 1950.