Independent of finding three different stamps: a neat blue center Zarate, a diffused blue center Zarate, and a dark blue 1L6 with at least one example from the family of wobbled kiss prints and even double prints of the center, the "SERVICIO OFICIAL" overprint is the same for all three major variants. Here is a sample:
Some neat printings:
Some diffused printings:
The 2P1L6 printing:
From the doubled center specimen:
