Dennis,
I'll toss my two cents worth into this. If I were you I would work the provenance of the pistol, not the pistol itself. Midden Heaps in fixed Indian villages are Archeological sites so there should be more documents, short of being stolen out of the midden by a thief of time using a back hoe. Archeology is done in layers, layers are documented, things can be dated by the material found around them. These are from such and such a time and so on. You say it was wrapped in oil cloth. textiles can be dated both by radio carbon dating and by more modern form of dating. Yes, this is expensive and probably out of the purview of anyone not rich or associated with a university. But a lot can be told about cloth by weave and by what it is woven out of and how the thread was prepared. The kind of "oil" used in making the cloth is also indicative of it's age and time. The question of why it was in the midden heap also comes into play, initial thought it was hidden there. Why? Did the tribe have European captives? Did they keep slaves? Did they have a hierarchy? Could it have been hidden there at a time after the tribe was gone for some reason, Anachronistic items in middens are an indication of this. No one of these items can date the pistol, but can narrow it down a whole lot.And then there is the big one: What, or most probably Who, rubbed the tribe out and why?
Firearms were valuable and therefore hung on to. If they needed repair, they were repaired without regard to keeping it original. I have a rifle that has been in my family since the revolution. It has no real value, other than sentimental, as it has been repaired and updated a lot since then. It is now percussion, I have no idea when the last lock on it was made, have no idea if the barrel and stock are original, or if the hardware was some how modified. What I really have is a frankengun that kept a branch of my family fed from the colonial times trough the great depression. So your pistol may have indeed been in the hands of a dutch corsair, and many to most of the above comments may apply. Like the others I don't think it is as early as 1650. In looking at the added on engraving on the frizzen, it looks vaguely Coptic--a collection of Christian cultures found in Africa, Syria, Armenia. The one on the left, which you drew as a asterisk looks like the loop continues to from a Coptic Chi-Rho
Another Version looks like an Asterisk
Looking at the photos I blew up and massaged a bit, it looks like it has a full ramrod in pipes along its underside. The best I could do makes it seem to be rather narrow, is it brass? I know nothing about what that could mean, maybe someone here does.
While I know I've given you no answers, Hopefully I've given you other places to look. 73.