Joe: Hunter Arms hand tags for 12 gauge specified 3 Dram with 1 1/4 oz. shot (1887 - about 1920), then 3 dram with 1 1/8 oz. shot (after 1920).

As you mention in the first post, there has been a repair of the left inferior finger of the head of the stock. Until you know the quality and extent of that repair, and whether the head of the stock was glasbedded, I would stick with 1 oz. target loads.
Please see
http://www.picturetrail.com/sfx/album/view/17090409

My big country pheasant gun is a 1906 12g 00. The head of the stock has been glasbedded, so I'm confident using B&P MB Classic 1 1/8 oz. at 1330 fps. For recreational skeet however I use B&P Competition One 7/8 oz at 1160 fps.

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