First Antique Chair

Just bought this chair. I don't know much about antiques, but would like to learn. The chair has a removable cushion which is most likely not the original seat(Busse Chair Seat). Screws are flathead. There is a marking/stamp on the bottom/back of chair, see photo. I am having difficulty reading the marking/stamp, but am hopeful someone will recognize it and point me in the right direction to learn more. I'm most curious about the age of the chair and who made it and where it was made. Thank you! Zach