What replacement breaker for a Gould GQF20MB panel?
Siemens has 2 lineages of panel: The ex-Murray line and  the ex-ITE line.  Yours is the latter.
I believe the QPs are indeed the right ones.  A Siemens dealer (electrical supply house) could cross-check it in their book to be sure. Or I have a feeling ThreePhaseEel will be along momentarily to same effect :)