These are French clasp knives. Friction folding knives (they also made similarly styled springback folders, but outside of Diderot's encyclopedia, I have yet to see one). These are the CLOSEST thing I have seen to the Taschenfeitel being used in 18th or 19th century North America (and it ain't that close).
This one has a poured pewter thingy on the end of the handle. Someone else posted a picture of archaeological finds, and on one of the knives you can see where the handle was rotted away, but the poured pewter remains. Most don't have that, of course.
These are found in large quantities in Canada and around the Great Lakes. There are different blade shapes: spear points, long clips, sheepsfoot. These all have a little cross tab on the blade that stops the blade against the handle when open. Handles would be horn and possibly wood, though I'm not sure I've seen an existing original wood handle so far. Sometimes the handles were "horn shaped" as above, other times carved into a sort of ball-butt design.
If you were a Frenchman or an Indian that traded with the French, you would no doubt have one of these. An English settler in Virginia? I'm thinking probably not so much. So far, all I have seen of folding knives in areas away from French trade have been spring back knives, generally of the Barlow variety (NOT the modern straight handle Barlow variety) or the basic style posted by Spence above.
In the early 19th century, things get a little more varied, and styles began changing. Outside of Barlow knives, I have little to offer as to what style is appropriate 1800-1840, as it's definitely not my time period of interest. The only way to find out is to research yourself.
My guess though, is that if you can find any folding knife with iron bolsters instead of brass or the ubiquitous nickel, that will be about as close as you'll ever get to an authentic early 19th century folding knife without having a custom knife made.
