Here's some text from a DEC monitor user manual:

    66 Hz:
	True color frame buffer module, model type PMAG-JA
	Smart frame buffer module, model type PMAGB-BA
	2D graphics accelerator module, model type PMAG-CA
	Low 3D graphics module, model type PMAG-DA
	Low 3D graphics plus module, model type PMAGB-DC
	Mid 3D graphics module, model type PMAG-EA
	Mid 3D graphics plus module, model type PMAGB-EC
	High 3D graphics module, model type PMAG-FA
    72 Hz:
	Monochrome frame buffer module, model type PMAG-AA
	True color frame buffer module, model type PMAGB-JA
	Smart frame buffer module, types PMAGB-BA, PMAGB-BC, PMAGB-BE
	Low 3D plus graphics module type PMAGB-DA
	Mid 3D plus graphics module type PMAGB-EA
	High 3D plus graphics module type PMAGB-FA

Simon.