No idea why that's the case. But I see it all the time and a friend owned a somewhat higher end firearms dealership for years and the Ducks Unlimited A5's and Pheasants Forever Browning's barely sold for what regular retail did, and never for more. MY personal hunch is that it's not a factory authorized change to the gun, but an aftermarket "badge" for promotional purposes. There is a lot out there about this, ie discussion:
https://castboolits.gunloads.com/arc.../t-269008.html
https://thefiringline.com/forums/arc...hp?t-3558.html
https://gundigest.com/more/classic-g...prices-auction