I think a person should have a lot of questions, and have them all answered, before considering putting money on a gun. Especially a used one. One photo doesn't tell me much of anything.
Personally, I don't like the mixed brass and iron, I don't care for brass on this type rifle at all but that's my opinion. It looks like it's nicely finished and put together though, and if you need a wrong sided rifle I know the options are limited, if it was right handed and I could get it 'cheap' and the bore was good I would be tempted.
IIRC Clark was a respected gunsmith from Canada. I recall some mention of his guns but because he wasn't American wasn't well known in the states. If you like this, I wouldn't hesitate.
I looked up his name and this is all I found. It looks like an L&R Durs Egg lock but I think he also made his own. J CLARK TORONTO FLINTLOCK LOCK ENGRAVED BLACK POWDER MUZZLELOADER WORKING | #3854214003
John Clark lived north of Toronto and died a couple of years ago. I bought the lock from him before he passed and haven’t used it. Gathering dust in my room sadly. I do have a 54 cal Lancaster rifle from one of Clark’s kits with the same lock that was largely assembled by a friend and finished by me. The swamped barrel balances beautifully and is bright. Haven’t shot it nearly enough.