Lexmark W850 Technical Reference Manual page 15

When these operators are used, it is equivalent to executing the following PostScript emulation sequence:
<< /PageSize [x y]/ImagingBBox null /Policies << /PageSize 0>> >>
setpagedevice
where x y are the PageSize in points.
Tray selected with tray operators
= Supported
X = Not supported
Operator Tray selected (corresponding image size is set) X860de, X862de, X862dte, X864de,
a4tray tray with A4-size paper
a5tray tray with A5-size paper
b5tray tray with B5-size paper
customtray tray with custom-size paper
executivetray tray with executive-size paper
foliotray tray with folio-size paper
legaltray tray with legal-size paper
lettertray tray with letter-size paper
oficiotray tray with oficio-size paper
b4tray tray with B4-size paper
a3tray tray with A3-size paper
11x17tray tray with 11 x 17-size paper
statementtray tray with statement-size paper
X864dhe
X
PostScript (PS) emulation
15
Printer models
W850n, W850dn
X