I wasn't aware of the Davenport, but there is a website that has the 23 tonners.
They apparently started their second generation of dieselization in 1952, ordering several 50 tonners over several years. THen U series and 32 tonners later.
The remaining engines include an 0-4-0T on apparently permanent display, and two 32 tonners (single engine end-cab, 4 axle, two traction motors with chain drive) that are still being used on a weekly? basis to haul water to several isolated villages that are company towns. All remaining equipment (at least 400 cars, plantation trackage, two 50 tons (#56 & 803), and at least five 32 tons have been scrapped; the engines sometime in the last couple of months. Four engines (said to be two U6B and two 50 ton with CAT 3508 engines) went to a 42" gauge RRDC operation in Africa a couple years ago. The 720 was built in 1957 and has some characteristics of the U series (air intakes) and a bigger fuel tank compared to SP1. In addition, the trucks are slightly different. SP1 had standard gauge trucks with narrow wheelsets, these have narrow gauge trucks and are only capable of 36"to 42" (and meter).
There was another division to the south, it apparently was closed earlier and the 720 is reported to be a transfer from it.