Ed, go to
http://parkerguns.org/ and click on "Research Letters" on the left column. It costs $60 for a non-member or $40 for a member. If you join the Parker Gun Collector's Association you not only get the letter for $20 less but you also get our quarterly glossy magazine (some people call it a "newsletter" but it is far beyond that). Members write technical articles, report on Parker related events with color photos, write stories of hunting trips and outings using Parker shotguns . . plus you can attend the Annual Meeting and Banquet and rub elbows with all the great guys who post here.
. . . but, at least send for the letter.
Dean