As this Thread still 'lives & breathes', just to add another dimension to the aperture (formal name for so-called "peep sights". As FN was first marketing its commercial modern Model 98 of the late forties onward design featuring solid left sidewall and and low scope bolt/safety configuration, they also offered the option of the "Armstrong Dual Range" aperture sight. A photo of one below. To me a bit more complex as 'officious' than useful. That aside, it was the "factory option" offered directly with the rifle rather than perhaps importer-intermediary product.
Also for clarity, just to reaffirm that the earliest version of that FN commercial action arrived on American shores "as advertised" in 1946. And of the corresponding rifles generally available in 1949, which bore standardized receiver sight mounting holes on right side of the Bridge, putting such installation just forward of the bolt handle.
The Lyman breed, in format of the Series ,48 ad 57 seemed far more popular, the fact of the Armstrong as more expensive along with features of little practically utility such as ability to choose between two aperture sizes, were of insufficient interest to cause price point justification. Yet rifles deemed ultimately "of Factory originality" repose in the Armstrong breed.
The Postscript that in late 1950-early 1951 the pre drilled scope mounting holes didn't escape the Factory as calculated by factory year markings, Best! John.
