Kiron made this lens. If the serial # starts with 22 it is a Kiron. I am impressed with the image quality of this little gem. It is sharp at 2.5 and razor sharp at f5.6. Color rendition is accurate. Colors are rich and separated well. Bokeh is surprisingly smooth. Bokeh fringing is minimal and reduced by f4. Chromatic aberrations are well controlled. Contrast is excellent. Micro contrast is surprisingly good. Images have a 3 dimensional feel. This lens also produces nice b/w images. See pic below. No effects were used.

Vivitar 28mm 2.5's regularly sell for $25 to $40. It is a bargain. Make sure you by one made by Kiron or Tokina. The Tokina version is also a very good lens.