Some dastardly BritishArmourer - or ANY Armourer - has taken the first top handguard out of the tray on the shelf and fitted it to your rifle when the orginal had cracked or broken. He didn't give a brass farthing where the part was made or even new! He just wanted the rifle in, repaired and out as fast as possible.
If he'd spent time rummaging through a huge box of handguards (or cocking pieces or trigger guards or foresight blades.........) looking for a specific part, the Armourer Sergeant would have said, none too politely, words to the effect '........ oh, deary me....., what a kindly thought but I feel you might spend your time more constructively just repairing the rifle and sending it out, back to the wanting soldier....' Or words to that effect.
Seriously, we didn't even CARE about what or who made the parts........