Letters and "lost' guns

[Keith Doty]

First, a nod to Mr. Bishop and the other research folks, they do a great job and are much appreciated. After seeing some photos of the Parker paperwork, I'm amazed at the amount of info they manage to wring out. I'd go blind/crazy!
I just got 2 of my applications for letters back as well as my checks. Very pleasantly surprised by the quick reply. Unfortunately neither gun had any available records. I was afraid of that when the serial numbers weren't listed but had to try. Does anyone know how many of the roughly 250,000 guns Parker made the records are missing for? I have 2 others that I find no listing for in the book. Is it worth the effort to apply for letters or is that info lost forever?