BTY..... I don't think the one above this isn't a M19 GMC but a later M42 DUSTER. It may not be listed right.
now i look at it closer i think you may be right
those tracks look too wide and it looks like a vietnam era photo
EDIT: hrrrm this is confusing the posted photo has the features of both
m42

m19

i think its an m19 just updated a little
in the posted photo the shadows show it is close to midday at the time of the photo which shows that the guns dont protrude past the front of the hull so it a rear mount and the frontal amour is of a m19
but in saying that the turret looks slightly different, the tracks are the same as a m42 and a cant see a spider web gunsight anywhere

IMO i think its a m19 updated for korea cause thephoto quality is too good for ww2 but i dont think m19 where used in vietnam