First day of Spring! And the temperature soared well into the 80's. What a day to test an old lens.

I had this Vivitar lens for a while but never used it. Zoom range is 28 mm to 210 mm, pretty versatile.
However, there was one big danger. See the PK-A/R designation on the side near the back? It was built to be used with a Ricoh SLR body. That means it came with an extra spring-loaded pin in the mount surface not used by Pentax. Try mounting it to a Pentax auto focus body and that pin will drop into the hole on the Pentax body mount for the focus coupling. And it will likely stay there, preventing you from removing the lens from the body, not quite on all the way, but not coming off either.
Most effective way of removing it is with a hacksaw. Trust me, I found this out about Ricoh lenses the hard way.

Fortunately I noticed the Ricoh designation and the pin this morning before mounting it to a Pentax *ist digital body. I was able to do the quick fix. The four screws holding the lens' mount part into the lens body are removed, and on the inside of the mount part, the flat spring pressing against the pin is pulled back and the pin is removed. The mount is reattached to the lens, careful that the stopdown linkage goes together correctly, and end of story. The lens is now compatible with Pentax bodies.

See photo below, I circled the location of the pin's hole in red.

So lens and camera united, I headed down to the Meramec River in Sunset Hills.

The Pentax *ist DSLR does not have any ant-shake feature, and all these images are hand held. I held the camera steady as I could, and shooting Aperture Priority, I took advantage of higher shutter speeds. Note the stop-action with the kids throwing rocks.
Lens is an older one and manual focus only. Camera body does have a focus confirm feature when shooting manually.

I tried to work the entire range of the zoom. Those buildings are across the river, in old town Fenton, 100 to 200 yards away.
Lens seemed to redeem itself at all distances.

So remember, when mounting a strange lens to a Pentax body, look at the mount first!

Please click on thumbnails to see enlarged.
All images are (c) 2017 E.J.Kowalski.
Thanks! Ed