This site below lists a very comprehensive information pertaining to Gravis Ultrasound.
https://pediaview.com/openpedia/Gravis_Ultras … _Play_.28PnP.29
1.) Different variants and models.
2.) Information of each variant
3.) OEM models
4.) External Links.

On a side noe, it was mentioned that some OEMs even palced 4MB sample roms on the cards!
Was it any better in terms of quality, I wonder.