Some of the pictures of Rebutia minuscula on Google appear to have "hairer" spines (I think they're just longer).
I came across Rebutia krainziana which looks a lot like yours, but I can't say I know enough about the genus to say definitively if either one is correct.
I'm a bit confused though because the database has it listed as Rebutia minuscula 'Krainziana' as though it is a cultivar of minuscula, but I can't seem to find that exact wording online.
Sorry, I thought I could be of help but I think I've just made myself more confused.
Planto
