I don't speak Czech. I've been translating (using Google) various Czech web sites to further my knowledge of the vz.24. There is a book by R.J. Berger but I believe its out of print.
But my guess for "HN 260" is that it means "Border Unit/Detachment 260". 'Hraničářský' is border in Czech/Slovak and 'notky' is entity in Slovak according to Google.
Where is this stamped on your pistol?
Front grip strap.





















































