(multi-coated) 
Vignetting = A Distortion = slight pincushion 
Aperture  Center    Corner 
f/8       B+        B 
Notes: Moderately high contrast; T stop close to f/8 (i.e., excellent light transmittance); relatively light with good balance on an OM body, without the necessity of a tripod collar; remarkable ease of focus for a slow telephoto.