"Pentax SMC-F 3.5-5.6/35-80mm"
If you mean the f3.5-4.5 35-70, this is known to be one of the good ones. Pentax can make consumer zooms that are both affordable and good. But they don't always do so.
This and the SMC F 70-210 f4-5.6 must have been terrific bargains in their day. (In fact, I have often suspected that they were intended to be a matched pair.) I don't know what they sold for when new, or whether users at the time knew what good lenses they were getting. I have the 70-210, and have sometimes wished for a reason to get the 35-70.
Joe
