I have a first generation swivo pedal, different foot plate, as per robcooks book, the three holes are so you can swivel the foot plate right or left with the connecting rod, depending on how you set up,or if your setting up on a small tight stage,hopethis helps

I think he is talking about the dimples in a triangle pattern and not the threaded holes that I think you are talking about.

Here’s the final result of the refurbishment. Thanks again to Bill Fulton for getting it cleaned up so well.