(single-coated)

minty sample; OM-1 with mirror lockup

Vignetting = B @ f/3.5, A- elsewise
Distortion = slight barrel
Aperture Center Corner
f/3.5    B+     B-
f/5.6    B+     B+
f/8      A-     A
f/11     A-     B+
f/16     A-     B+
Notes: Moderately low contrast @ f/3.5, moderately high contrast elsewise.

sample that was dropped, with a bent filter rim; OM-1 with mirror lockup
Vignetting = B- @ f/3.5, B @ f/5.6, B+ @ f/8
Distortion = moderate barrel
Aperture Center Corner
f/3.5    C+     C
f/5.6    B      A-
f/8      A-     A
f/11     B+     B
f/16     B+     B
Notes: Low contrast image at f/16, f/11, f/3.5, although high resolution of high contrast details at center of field; moderate contrast at mid apertures; optimum at f/8. Possible element decentering?