Perforations of the 10c Rivadavia Red

After ignoring this topic for a very long time (try 15 years), and receiving a Stanley Gibbons transparent strip to measure watermarks, I have made some measurements of the 10c Rivadavia Red:

Small, slightly irregular holes:

Type I horizontal.



Type I vertical as if it was 13.5, which it isn't.



Type I vertical measured correctly, looks like 13.1, and not 13.



Type II horizontal



Type II vertical



Medium, regular holes:

Type II horizontal



Type II vertical



After these measurements, I now realize why I am unable to separate the two vertical perforations with the naked eye:

1. The 13 perforation is from the irregular grid with small holes, and the measurement is not exactly 13.5 or 13.
2. The difference between 13.1 and 13.4 is VERY small.

I wonder if the other stamps from the first batch (October 1, 1935) are also found with the 'almost 13' vertical perforation?