What I'm trying to get at is that we can't see the badge holes clearly. I see something sticking out one side that makes me wonder if it's a ding or if the frame is drilled for the diagonal badge, which would confirm the frame to be Silverking with that era badge, right?
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If it has no badge holes, shroud and tank fitment would be the logical explanation.
Everything is adding up so far as patina at the crank hanger, fender rivets, and someone(you) confirming such a model existed with documentation. But I like to comb over something before I consider using the 4 letter R word. If it has had a head badge removed, what says the S/N badge hasn't been tampered with, you know?