As the last couple of posts suggested, you do want to make sure the rifle is unloaded. First thing.
That's actually a pretty nice rifle, I would say probably built by a talented amateur. The wood is beautiful, and the inletting is very good. There are a few things I don't think you would see on a real professional build... The orientation of the patch box is at a funny angle, for example. Also, the oversized and over decorated side plate would not have come out of a really professional shop. As brother Cowboy pointed out, "Grizz" is a very common nickname or alias in the buckskinner crowd, so that may not help much with identification. Unless the builder is well recognized, a late 20th-early 21st century rifle like this will not bring much on the resale market.
However, Siler locks, like this one, are excellent. The wood is first-rate, and apart from a couple of little quirks as noted in the previous paragraph, the rifle looks solidly built. I would be surprised if any builder would combine a lock and stock like that with anything but a good quality barrel. As mentioned in one of the posts above, there may be some markings on the underside of the barrel, concealed by the stock. That should give you an idea of who made the barrel, and its bore size. The point of all of this is that your rifle should be a shooter! I don't think it's value would be diminished by shooting it, provided it is properly cleaned after each shooting session, and stored properly in between. It could very well become a favorite of a left-handed shooter who wants something of a little better quality than the average import, without investing in a new custom build.
I would recommend that you verify that the rifle is unloaded, as Pietro described, then carefully dismount the barrel. Look all over the outside of it with a magnifying glass. Lift the lid of the patch box and look inside, and remove the butt plate and look under it. Builders sometimes leave little written "surprises" or identifying marks in those places. You might also look in the barrel channel of the stock, to see if anything is written there. Report back with your findings and let's see if we can piece together a little more of this interesting rifle's story.
Best regards,
Notchy Bob