The F48 class, of which there were sixty, were built between 1900 and 1903 at Stratford Works, and had round-top fireboxes of the same type as used on the Class S46Claude Hamilton 4-4-0s. No. 1189 was built instead with a Belpaire firebox, being the first Great Eastern locomotive to be so fitted. This was done as a comparative experiment against the regular round-top firebox. The experiment was a success and a further thirty locomotives constructed later were fitted with Belpaire fireboxes and termed the G58 class.
From 1921, all the round-top boilers were replaced by the Belpaire type, the majority being superheated. Sixteen had been reboilered by the Great Eastern before the grouping of 1923. The remaining forty-three were reboilered by the London and North Eastern Railway and were re-classified J17. All had been dealt with by 1932, whereupon the Class J16 ceased to exist.