You can look up a whole lot of stuff about High Powers on the Internet. John Browning began the design back in the 1920's, but died before it was finalized. FN finished it, and put it on the market in 1935. It was the first "high capacity" military pistol (the magazine holds 13 rounds) and sold all over Europe. During WWII, the Germans forced FN to continue making it for them, while a factory in Canada tooled up to make a copy for the Allies.
A lot of armies either kept using it or adopted it after the war, and some still do, although it has been getting replaced by more modern guns. FN still makes it, and so do Argentina and India, at least.
This one has factory target sights, not the military fixed sights.
I wonder what the "S. SH" on the grips mean? I would not be surprised if it was Iraqi loot from Kuwait, but that's idle speculation.
Thanks for putting up a first-rate photo!
PS - FN revised the design in minor ways in the 1950's to make it easier to manufacture. This gun was made after those changes - the extractor is the most obvious change.