Thanks, @NorthFork ! This has given me a reason to hit the books. Since my last post, I've looked through several, including The Trade Gun Sketchbook, For Trade and Treaty (pretty carefully for those two), Hamilton's Colonial Frontier Guns and Indian Trade Guns (...but not very thoroughly), and Hanson's The Northwest Gun. I did not see any images or mention of turtle front sights. Charles Hanson said, "The standard fusil front sight was a low iron blade set two or three inches back from the muzzle" (page 40). I was surprised to learn that the Bumford trade gun (early English) has a brass front sight dovetailed in place, and Hamilton described a Type G gun with a "half oval brass blade." I believe the Chief's grade guns often had what is called a "spider" front sight, with four arms spreading out from the blade and inset in the top of the barrel.Fair enough. I have several books detailing trade arms. Most have detailed pictures. Without digging them out, now that I really think about it, I think you are right.
So, no turtles... yet. However, I think those of us who have guns with turtle front sights ought to just shoot them and enjoy them. There is no way we will recapture every historic detail.
Funny story... I ordered a Northwest gun from North Star West maybe eight or nine years ago. I found pictures of an original Barnett I liked,and I called Matt and discussed all the details. He built it just like I wanted. It was some time after I received the gun that I discovered I had asked him to make a copy of a of an original Belgian counterfeit of a Barnett! It's a great gun, though. I love it.
Notchy Bob