Chap on Twatter posted this. Tracked carriage ring any bells? I'm pretty sure it's the same piece, Duckbills, not SP, but haven't got much further. They were certainly very thorough with shelling Manilla. One-off? Standard swampy carriage? Nothing in Hogg so far, and he's usually the man for this stuff. And from here: Dad's War Photos: Adventures in the South Pacific
Ah, sorry. Hogg: Materiel T16 & T17: Collective term for cannon & Free-rolling tracked suspension for use on difficult terrain. T16 Used 2 complete medium tank susp.units, T17 used lighter version. T17ei 'modified'. One T17E1 set issued to FAB in the Pacific early '45. Sorry.
Oh balls. Hogg old, Zaloga newer & likely better on US gear: US Field Artillery of World War II And on tractors. It's behind an M35 in the second shot. I wouldn't read too much into what was deffo where.