For those who may not know:
Specifically that's a D&RG class 42, Baldwin class 8-18½-C d2; 12x18 cylinders, 45 inch driving wheels (40 inch centers), 6,365 pounds tractive effort. The D&RG owned a dozen of these. The photo's pretty fuzzy so it's hard to see the trim, but this one appears to be in its original colors still (names usually disappeared pretty early). Mentally color it green with a grey bare metal boiler.
New Zealand Railway almost bought very similar 8-18½-C locomotives for its own use, going so far as to place a preliminary order, but ultimately went with the Rogers 2-4-2's instead.