To the button Gurus from around the world-I need help on an ID :-)

[fishbone3d]

On the back it says "Imperial Duality" or "Duality Imperial" Who knows? My guess is as good s the next guy's It was very green when I excavated it from it's resting place. I am guessing it is probably brass. I cleaned it off when I got home with a soft brush to see the detail. Thank you in advance to anyone who has some information on this item.

 

[creskol]

Probably says Imperial Quality

 

[fishbone3d]

Probably says Imperial Quality

I could see that.

 

[TheCannonballGuy]

"Imperial" in the backmark of a 1-piece "flat button" means it is British-made, and most likely from the 1820s-to-1840s.