The United States Army Transportation Corps (USATC) S100 Class is a 0-6-0T steam locomotive that was designed for switching (shunting) duties in Europe and North Africa during World War II.

After the war, they were used on railways in Austria, China, Egypt, France, Great Britain, Greece, Iran, Iraq, Israel, Italy, the Netherlands, Palestine, the United States, and Yugoslavia.

[4] Other S100's entered British industrial use with the National Coal Board, Longmoor Military Railway, Austin Motor Company and others.

[9] The Southern Railway (UK) bought 15 S100's (14 for operational use and one for spare parts) and designated them USA Class.

[11][12] By 1946 the SR needed either to renew or replace the ageing B4, D1 and E1 class tanks used in Southampton Docks, but Eastleigh Works was not in a position to do so in a timely manner or at an economic price.

[10][page needed] The railway's Chief mechanical engineer, Oliver Bulleid therefore inspected the surplus War Department tank locomotives.

The Hunslet Austerity 0-6-0ST locomotives stored at the Longmoor Military Railway proved to be unsuitable for dock work because of their 11 ft 0 in (3.35 m) wheelbase and inside cylinders; also many of the survivors were in poor condition.

The railway therefore accepted one Porter locomotive at a reduced price and purchased another to provide spare parts.

Following purchase, members of the class were fitted with steam heating, vacuum ejectors, sliding cab windows, additional lamp irons and new cylinder drain cocks.

[14][10][page needed] Further modifications became necessary once the locomotives started to enter traffic, including large roof-top ventilators, British-style regulators (as built they had US-style pull-out ones), three rectangular cab-front lookout windows, extended coal bunkers, separate steam and vacuum brake controls and wooden tip-up seats.

They performed well and were popular with the footplatemen, but the limited bunker capacity often necessitated the provision of relief engines for some of the longer duties.

[16] A more serious issue was the condition of the steel fireboxes originally fitted to the class which rusted and fatigued quickly.

The survivors were used for informal departmental purposes such as providing steam heating at Southampton or shunting at Eastleigh Motive Power Depot, before the withdrawal.

Although malachite painted 30064 was substituted in 1964[19] it soon returned to Eastleigh,later having a short spell at Meldon Quarry near Okehampton (August - October 1966) when it was the last steam locomotive active on the Western Region.

[22] Nine examples remained in service until March 1967[23] and five of these survived until the end of steam on the Southern Region four months later.

However, before they could make their journey, their bearings ran hot and were declared "unfit for travel" which led to the two tank engines being dumped at Tonbridge.

JŽ added to their class 62 by ordering several similar examples from Đuro Đaković (factory) of Slavonski Brod, Croatia.

This gives the steam pipes a shoulder instead of being straight, and requires smaller domes with a flatter top to fit JŽ's loading gauge.