A friend purchased a gun that was very similar to what you described - best quality Belgian sidelock (hidden third bite, articulated front trigger, rounded lumps, 100% fine floral engraving, high quality piece of dark walnut, very finely polished, deep blued barrels). It was made by Faulkner, which is not a known name in the US. The gun sat around KTP for a year or so until he found and paid $5-6k for it. It was as nice as any Lebeau I have seen selling for 5x as much.
If you are buying to shoot rather than collect, guns like that are a great value, assuming everything checks out. Start with the proofmarks and any other barrel stamps.
