I have a VIVITAR 28-70mm f3.5-4.8 Auto Zoom MC Macro Focussing.
Made in Japan.
Mount: Pentax PK-A/R (also Ricoh, Sears, Chinon etc)
I have made good use of this lens for general photography and some astrophotography.
Other than some typical vignetting (at long exposures), it is great.
I used this lens to take several wide-angle photos of the recent planetary alignment (using 28mm w/Ricoh KR5 SuperII)
Optically excellent. The zoom barrel is a bit loose (moves due to gravity). Focussing is pretty firm/smooth.
$40 Shipped. Money Order please.