Wow Kirk. That's like a blast from my past back in the northeast. There was a lot of that on the lower end houses in PA. I wasn't a home inspector back then, but I'm pretty sure it was just an asphalt shingle designed for vertical siding. I don't know what they layered behind it, probably just tar paper. I think the majority of them have been covered with vinyl or aluminum siding by now.

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Jim Robinson
New Mexico, USA