PolygonOffset and SGI Hardware

In attempting to write some hardware independent code (PC and UNIX workstation) using glPolygonOffset, I have found that the output on SGI graphics cards is incorrect (i.e. missing polygons or strange stripy effects). Does all SGI graphics hardware support glPolygonOffset and if not how can my program detect which do?

I already check for OpenGL version 1.1 through #ifdefs.

When you look for #ifdefs, you’re looking at the header files, which might be 1.1 compliant. It is still possible though, that your hardware driver is 1.0

I presume that means I need to check glQueryVersion as well? Thanks for the hint.