An interesting find. Going from Volvo's own site, your dating appears to conform:
http://www.volvo.com/trucks/na/en-us/about_us/history/1976 - Volvo F613 medium duty truck launched
As for the maker, it is difficult to say. It appears they might have used a textured glass to begin with, so if the pattern can be identified this might help, although I am assuming it could be a US rolled-plate glass. The shape does not appear to be one produced by Houze, so the other US company to explore is Behrenberg:
http://www.behrenbergglass.com/The shape and pointy corners do seem to conform to their current product range and I note they offer textured glass

Also worth checking the size and thickness: Behrenberg appear to offer a 3/16-in textured range (approx. 5mm), although what was available c.1980 could have been quite different.
EDIT: Download the catalogue pages here:
http://www.behrenbergglass.com/catalogPage.htm