One of these http://www.ebay.co.uk/itm/HO-OO-Triang-Wind-Up-Shunter-Switcher-Clockwork-Model-Railway-/160990314733?pt=Model_RR_Trains&hash=item257bc540ed, a custard and cream carriage (passenger car) and a handful of freight wagons on an oval of track. The 'square' dome on the the loco's boiler hides the clockwork spring.