Manganos, you're welcome. : ) By the way, your post correcting the name to Oxfordshire instead of Yorkshire arrived at the forum while I was typing, so I didn't get to see it until after I made my post.
In it, I said I knew somebody had dug a button with that emblem recently and posted an ID-request about it, and that I had replied to it. I did some searching and I found that ID-request.
"Can anyone ID this button?" by NealNoINIronBrigade back on sept.16, 2005 ...and I answered it on Feb. 9, 2006 (just a few days after I first got told about the Findmall forums). As of tonight (Sunday) that thread is close to the bottom of Page 3 of this forum (Relic Hunting).
You might want to go to that thread, to see the photo Neal posted of his button. I mention that photo because I think it shows the Rev-War era version of the button. I'm almost certain that your button (and mine) are not Rev-War era, but at least 1820s or MUCH later, because ours are "two-piece" brass buttons. Mine has an iron back ...which may be the reason the back is missing out of yours. But who knows for sure? ;-)
As I said, with no back - or a heavily rust-coated iron back like mine's - determining a date-of-manufacture for a Foreign button gets far more difficult. I suspect it's going to require a reference-book of British Military Buttons. I'll do a search for one, and you do that also, please.
Meanwhile, here is something I said to Neal in my reply to him on Feb. 9th, 2006.
"You can see a photo of the emblem on your button - and read the Oxfordshire & Buckinghamshire (a.k.a. "Ox & Bucks") regiment's history) at:
[www.royalgreenjackets.co.uk]
Regards,
TheCannonballGuy (Pete George)