Chuck, You switched numbers. It's 17895, not 17985. It is a 3 frame 10ga and measures 2 1/2. I also have 51092, 3 frame 10ga, measures 2 1/2 as well.
I agree mystery solved.
__________________
"Double guns are a sport and a pastime built into a beautiful package to which I attach myself when entering the great theater of autumn, those days now grow more precious because we are given so few".. Robin Lacy