Can't tell you how their products stacked up against the competition, sorry.
In the 1965-1975 time frame Sun was a fairly common name for 3rd party import lenses. I wouldn't say they were a really big player, but they were in the mix. Possibly more common outside the US. I think they were a manufacturer, not just a brand name, and have since concentrated on medical optics. They may be known today as:
SUN OPTICAL CO. LTD.
802-1 SUGIMOTO-CHO
SABAE CITY, FUKUI, 916 JA
077-852-8155 / 077-852-8155
or these guys:
Sun Optical Co., Ltd.
Tel: 886-2-23414698
Fax: 886-2-23412167
E-mail:
sun94@ms6.hinet.netI bought a huge Sun (190-430mm)zoom in 1969. I still have thus blunderbuss. I used it a lot, actually. Hoping a curator from a big Japanese optical museum will read this and offer me big buckos. Planning my golden years around it, matter of fact.
Now, get back to your studies.