I found this from a post I copied some time ago.
Forgot who posted the specs, but thanks.
"The holes are #6-48 size. Starting at the recoil lug at the back for zero. You can use an edge finder for that. 1st hole going forward is at .562. 2nd hole is at 1.224, third hole is at 1.824. They are centered between the sides of the slot that holds the rear sight tang."
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