Hi vintage scope. I'm sorry you've waited a year & a half for a response to your question........I'm afraid I don't look at stickies very often, as a rule! Re the bracket thumb screws, I don't know the significance for sure of those bearing a broad arrow, but suspect that they may be replacements, quite possibly of post-WW2 manufacture. I have a few of them that came in a small batch of original thumb screws from an old gunsmith some years ago.