The real helmets may not have used real Bordens. At least nothing exact has been found.
As Syper points out, several modern 3 hole connectors have the two small holes the same size which is incorrect. Other found Bordens have the correct 3 different-sized holes, but as shown in the pictures above, the holes are not positioned exactly like the ones on the real helmets.
Furthermore the image of the real Borden above has been mirrored so to compare against the part used on the PP3 helmet. To make your real Borden have the correct hole orientation you must cut it down and use the cut side facing out. Then you are left with a brass surface (Bordens are stainless steel plated brass) and the holes have now lost the chamfers present on the uncut side.
Since none of the original helmet's Bordens are brass I think that either the parts must have had the opposite orientation from any we have found in the present day; or that they were machined parts made to be similar to a found part.
The supertrooper sheets specifically call the part "1 dental "greebly" - Brian Archer" but refers to other similar details used on the helmets as "2 dentist drills - Brian Archer"
Why specifically call the cheek detail a "greebly" ? No idea. Maybe they just didnt know that the part was a Borden Connector. Or maybe it wasn't....
Anyway the point is I urge people who are striving for accuracy to not buy any real Bordens (inaccurate) and go with the stainless steel replica JodoKast89 is going to make.