AFIK:

Sigma Designs was a swedish company that manufactured/marketed hardware
products for the mac market in the early 1990s. I remember reading about
them in MacWorld shortly after I bought my LC in '92/'93. 

They advertised on-the-fly resolution switching and large virtual
desktops long befor macos could do such things. The products were well
received, if esoteric. By 1995, they seemed to have dissapeared. 

The card you found is probobly reporting the odd resolution as part of a
hardware based virtual desktop with pan/zoom capapbilities. I remember
they made two monitors, a full page portrait display and a 16inch
landscape display (both greyscale). 

They also manufactuured a stuffit or diskdoubler based compression
coprocessor.

Casey
n3506886

> > macvid0 at nubus0: Sigma Designs L-View
> > macvid0: 832 x 600, monochrome
...
> I bet it's a proprietary connector.
...
> Hmm. I'd worry that the video card's not a standard EGA/CGA output
...
> I bet it's old and proprietary. People did weird things in the late
> 80's, and since the mac was/is flexable about these things, they got
> it to work.