Saddle Tank vs. Side Tank nomenclature - Model Railroader Magazine

CNJ831

... large examples of side tank engines were employed as communter locomotives (in some cases also referred to as "suburban" bi-directional type) in early 20th century America.

CNJ:

One of the more elegant examples of this is the CNJ J1 2-6-2T, as I'm sure you'll agree. These apparently survived long enough to be reclassified SU23 after the war, but I don't know what they were used for by that time...were they still hauling commuter trains? Information on these is tough to find.

It's a pity none of these survived, although they might have ended up in Thomas paint. >:)  I wouldn't mind acquiring or building one; it would be a good fit for my little railroad.

(Photo below taken in 1938, from northeast.railfan.net)