Wayne, I am sorry, we were both composing and posting at the same time. The lock you show is just too early in style to have been made originally as a percussion lock. If the link works for you you will see the similarity is style of the plate which is at least late 18th Century. Shortly after this the Dutch started copying the French M1777's style for their military guns. With it's inclined brass pan, this would have been even more distinctive.
But, let me say this, you have the lock in hand and I certainly do not wish to argue with what you say you can see up close, however I do see a screw in your photo where it should be located for a frizzen. Proper conversion will often hide this very well on the face of the plate and even on the back. If I am wrong, I do apologize and will step out of the conversation. But the Dutch were very competent gun makers, for both military and civilian use, and they stayed up right along with the French who were the leaders of gun production and improvement worldwide in the late 18th and early 19th Centuries. Just my opinion, of course, for all that's worth, but this lock is just too early in style to have been anything other than flint.
Could we see a picture or pictures of the entire firearm?