Why is the Arabic numeral “6” different from one Pam to another?
The simple/short answer, with only a few exceptions, is that the “open 6” is representative of Historical Pams [112, 111, et al], whereas the “closed 6” is representative of Contemporary Pams [104, 123 et al]. Furthermore, the Historicals are open we presume because of the early usage of the sandwich dial that had actual cut outs to allow the luminous material to be visible.
