I bought a 70-200mm Osawa Mk-II zoom for my Pentax kit back in High school. I was never too impressed with it. It wasn't bad - just never found much use for it. It was inexpensive and fairly well built but with a maximum aperature of f4.5, just not very interesting or useful.
I much prefer the 135mm 1:2.5 SMC Pentax optic.