https://www.staraya-moneta.ru/lib/13311/ - article in Russian. See chapter about 1970s. If you have way to run surface metal test, check amount of zinc in alloy. Article tells that fakes are made of brass.
If you decide to collect Khorezm rubles, get a book about them first. You need the way to tell which variant you are buying before paying for it.
Thank you for your links. So it looks like there are graded coins with the same combination of obverse and reverse as I have, which is good. I guess I will just need to get mine checked by an expert