The proof mark on the barrel is a Belgian mark indicating a "rifled barrel". Many Belgian made guns, barrels and parts were imported back in the early 1800's.
edit - after checking some of my "pile of papers" I found that, that particular mark was first used in 1852 by the Liege proof house (Belgium) - so while this is on a flintlock, which would "tend' to indicate an 1830's or older piece, the barrel was (proofed), minimally 20 years into the percussion cap era.
(and what you note as a circle is actually a crown that is so distorted it's tough to make it out)
The marking on the lock could be any of a number of things. It could be the lock maker, the gun maker, the hardware store that the lock was bought from, the importer of the lock or even the guy who originally owned it.
A picture of the entire rifle might help narrow down what exactly you have.