I was curious for this answer as well. My first ever quality set of wheels hand built for me in 1987 used Trek Matrix branded rims with Suntour XC cartridge bearing hubs (nutted axles to begin with, later swapped to hollow axles with QR) and overkill 36 spokes. Black anodized rims. I figure I put many thousands of miles on them before the side walls started to give way due to grit wearing away at the aluminum.
Not surprised to hear Sun made them, great set of wheels