hi, Rupiah
most of them are HPY around 2.5 to 2.6 M and HPK 4.7 to 4.8 m. all of their sticks have stars! seeing that, i don't think of checking further.
The range is huge 100,000 in each case but based on my data all notes in that range would be expected to have stars.
I have reached a point in my research where I can predict with 75% accuracy whether a certain note in the HP? prefix will have a star or not based on its prefix and serial number. My accuracy increases to 85% if I am able to see the back of the note but with the stick covered.
The star effect happens because of missing ink in some microprinting pattern that is used in the back of the note. The fact that the ink is missed in precisely the same location in almost a predictable fashion is intriguing. I have no answer to explain the reason for it although one can assume that it is related to some aspect of printing.
Finally in research all facts are good news. I am not hung up on any theory one way or the other but I have gotten a kick out of doing this and in the process I have learnt a lot of intricate details about the design of our notes.
So thank you