Bill, an additonal feature of the 39D is the barrel band instead of forend cap. My dad's had one since '75 I think, and I've spent hours looking through it's Lyman peep.
Another model that he's got that's very rare, is the Carbine. It's essentially a Mountie with a shorter barrel (can't remember the length, and a half-length magazine. I think it was a one or two year production in about '67.
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