With my name being Graham Lamb and having a father named William, I took a mild interest in rifles built by the Lamb's in Jamestown when I stumbled across them.
Likewise, at first look my initial reaction also was - no, nothing like William's rifles, at least the few that I collected pics of.
But, looking through the rest of my "Lamb collection" I do see a rifle by Anderson Lamb (Jamestown ca 1850) that does resemble this rifle (if you squint a little).
I don't know what his relationship was to William's clan but can maybe assume they were related somehow and there (could) have been some influence there, or did Anderson obtain a barrel from his cousin (or whatever) and build a rifle??
Anyhow, here's the rifle (sorry - a couple of less than ideal pics), but must say I see a fair bit of "similarity").
P.S. if one turns up stamped G.A. Lamb, that is one of my renditions, and I'm not related to those in Jamestown that I know of