Sorry mate since emigrating to Holland 50 years ago, I have trouble remembering what n/s and o/s is!
Is "nsf" left ? Think so?
A right hand ZT 190 caliper will fit the left hand side of your 260, and vice versa
Maybe better to use terms like "LH" and "RH". Much easier, and importantly that is how MGR designated all the bits!
David.