I have always found overprints to be a very tricky field. They attract forgerers and collectors get easily deceived. It may not be the amount of money involved for a single forged stamp; 500 copies of a relatively scarce item sold to collectors who will get the illusion to have a complete collection will also pay off....
A unwritten rule in philately used to be not to describe nor publish in detail a particular overprint - real of fake - in order to prevent further forgeries. That may have been practical 75 years ago when typographical printing was still around, but nowadays any forgerer will try modern methods to produce their products and these should get recognised more easily
The Overprints are in 2 groups since 1913: no serif <-> with serif; however in the no serif group I see another division of circle points <=> square points. Whereas the serif/no serif division found its way into the catalogues, I do not see any reference to the circled vs squared points in the catalogues....
For the PyR only the overprints with serifs are relevant and all points are circles, .. at least....?