ok, in the original picture (I should do this in the first place)the 
militar sitting has three bars in the hat and so on the shoulders; the 
other, with an eagle badge has two capital letters on the collar C and 
P. In the site www.en.wikipedia.org I found for the mexican army that 
three bars mean Capitan Segundo (Senior Captain)and three bars with 
the one in the middle been shorter means Capitan Primero (Captain) so 
I have know why the eagle on the chest and CP on the collar.