Here's a thought after rereading this thread. There's a range of Uighuir polar stars without a mintmark:
1) just a manufacturing error... or more to it? a manufacturing error over such a long range of polar stars seems odd to me
2) now, there's a small range (or rather, a sub-range within the range without a mintmark) where manually a mintmark has been added... 1710-1776 based on known examples... would there really be an operator who thought "oh, we have been forgetting to put mintmarks on for several hundred polar stars, i'll put them on for a few"
This is an interesting mystery which hopefully some day will be resolved... In any case, I think the manual mintmarks are a sub-type within the "no mintmark" type.