I showed you a value from the 1950 set to commemorate the centenary of San Martín's death some days ago here. The set is a mix of photogravure stamps depicting "scenes", like the one in that post, and stamps depicting portraits of San Martín. The latter are the nicest because they are recess-printed and very well executed, I think. This here is my favourite.

It's based on a painting by J. B. Madou. There is a lovely miniature sheet with all four portraits on, but I haven't got it so I can't show it. I hope to one day lay my hands on it as it's really worth having, I think (just to please the eye, mind). So if and when I do, I'll let you have a look!