The first one:
A 21.0x25.4mm *
C12 1/2:13 1/2 16/14 = 12.558:13.333 typo (1908-), offset-litho (1916- ),
C13 1/2:13 1/2 17/14 = 13.386:13.333 typo (1908), offset-litho (1916- )
* it has never been given in exact terms as usually the design measurements seemed to be more important
It is rather important as we can be mislead by our perforation gauges.... 21.0mm an 25.4mm is on the basis of a half sheet of 10x10 of the 20c JSM. Using 25.3mm the gauges of the longer side will be 12.648 and 13.439; using 25.2mm 12,698 and 13,492.Rounding off for the 17/14 version, the closest quarter would be 13.50:13.25 in all cases; the 16/14 version however would only give 12.50:13.25 in the first case and 12.75:13.25 in the other two!
However, as the horizontal direction of paper started to occur later on - not for the ovals yet! - shrinkage of paper would only affect the vertical gauge for stamps with a horizontal direction of paper [eje de enrollamiento].....
