When the FN FAL was first being sold, many militaries that bought it opted to mount optics on a small percentage of their rifles. These military setups used a variety of different optics and mounts, and led FN to develop their own OEM solution. By the 1970s, the FN industrial conglomerate including an optics workshop, and so they produced their own 4x optics for the FAL and FNC rifles. We have an example of one here today, a 4x28mm FN scope on an FAL. Note that the lack of specific designation on the BDC cam indicated that it is a 7.62x51mm BDC; the ones intended for 5.56mm in the FNC rifles are marked “SS109”, “109” or “92”, depending on the 5.56mm loading they are calibrated for.
Sold for $4,600 at the December 2019 RIA Premier auction.