You certainly appear to be correct. Good job!Very nice. As soon as I saw the engraving and seen it was brass I knew it was old. 1700s.
This is some info I found on a brass pistol guard. Maybe this is somewhere to start looking.
Ketland & Co
Brass Barrel English Flintlock Pistol with Ketland Lock and London Barrel Marking
.60 caliber, 9-inch smoothbore barrel engraved LONDON and with British proofmarks; border-engraved lock marked KETLAND/& CO. Brass mounted walnut stock; acorn finial to trigger guard.