Tank Steam Locomotives, sometimes called Saddle Tank Steam Locomotives, were engines that had no need of a Tender to carry stuff like water and coal. The reserve of water was in tanks on either side of the boiler and a limited supply of coal was stored at the back of the engine. These Steam Locomotives were used for short haul and the wonderful work of shunting, and in my view they are the cream of Steam Locomotive crop, especially when you pause briefly to consider that an electric model train doesn't like water and there's really no need for coal.
There was a big thing for running steam trains on oil. The Tenders for such
locomotives were ugly in the extreme, they just look unnatural and totally
destroy the glamour of the entire Steam Locomotive experience. Of course in the
good old days, stray sparks from the engine's chimney would do things like cause
fires in someone's Wheat field. Modern equivalent would probably be something
like a Jumbo Jet engine landing on the Vegetable Plot. The point is the French
Google-bot must have had a well deserved day off, it's now returned with a
vengeance and I'm doing my very best to entertain it with the kind of bromide
that hopefully substitutes for watching paint dry in the Google-bot community.