Jerry, Sorry, but my scanner is in the crapper.
The one place that I've seen this actually illustrated is in Chuck Schmidt's reproduction of the 1963 Ron Kitching Catalogue. Perhaps someone can share a scan of page 10 with everyone.
What the illustration shows, is a large outer chainring with an inner band linking the 6 arms and right at the ring/arm intersections the 6 holes are drilled through. Then within 3 of the 6 trapezoid windows between the arms, there are short 'tangs' extending inward.
Before examining that very small illustration for a second time [just now], it had assumed these tabs must logically suggest that these 3 connection points must have been allowed for fastening to a something with greater BCD than 116 mm. But, this does not appear to be the case, after all; they seem to be simply additional alloy material, added to furher support the drillings along the thin inner band. Yes, all 9 holes appear to be right at the intersects with the band.
So, this still raises the question: what the heck were 3 additional equidistant drillings needed for?
I think that perhaps the other 3 were actually tapped / threaded holes, or at least bored in a different diameter than the other 6 - and were intended to better support an original 3-arm steel crank's threaded screws.
~ Just my guess.
Bob Hanson, Albuquerque, New Mexico, USA