preset aperture with 8 iris blades ($60 @2014), the oldest? 35mm from Minolta

The ring with that white dot can set a desired F-stop, you can rotate the metal
ring with a lug to desired F-stop. If you set the white dot to F22, the lens has
basically a stepless aperture control. This metal ring was replaced as a preview
button at the later MC Rokkor era. It is a well made lens even for today.

Its optical design is quite likely Biometar/Xenotar type, though not 100% certain.
See > http://spiral-m42.blogspot.ca/2011/12/carl-zeiss-jena-biometar-80mm-f28.html
New info > http://www.massimoscottinelweb.com/Minolta%20produz.obiettivi.htm
According to this new info, this lens' optical design is NOT Biometar/Xenotar type.