Lexmark X422 Technical Reference Manual page 219

resolution
queries the resolution for the current print job. An integer is returned on the
stack:
300 dpi is set to On
600 dpi is set to On
1200 dpi is set to On
This operator is equivalent to executing the following PostScript emulation
sequence:
currentpagedevice /HWResolution get 0 get
Error: stackoverflow
revision
queries the Revision system parameter. An integer is returned on the stack to
indicate the revision level.
Error: stackoverflow
4-45
PostScript