Hi Rudolfo,
I expect one of the real experts, like Marc or Fritz, will tell you that there are all kinds of minor errors and glitches on the 1868 Full Face Hidalgos that don't amount to a hill of frijoles.
Based on the minor differences in the various transfer types, some of these guys can even tell you from which position, from which plate, from which year, this particular stamp came from. I have been amazed at the amount of detail that is known (by some people) about these stamps.
Best regards,
James