Change . . . shells.
2) [dihutenosa] 7-9-2007(97): This is a freight train that runs on spare change. Imagine getting on the freight train with a bunch of spare change. You put in some change and it starts up…goes for a few minutes, then starts to slow down. You look at the slot..there’s actually a slot for spare change and one for regular shells. Your call, but it seems to prefer spare change over shells.
3) [ruisu] 17-11-2007(46): Countries like to change money by trading freight.
4) [herman] 20-3-2009(36): This is also commonly used to mean currency, which is easier to remember given the kanji I think. When you travel abroad you change your clams into the local currency. Easy breezy.
5) [Neobeo] 13-12-2008(13): You catch the freight train, but suddenly realise you did not bring enough money. You turn out your pockets to show the inspector that you have nothing but spare change.