I think the test at this link explains a lot.
and the silver M39 version is Here.
For f 2 to soft. Stopped down from f 4 and above does not show anything special. (only for my copy), poor colors.
No precise sharpening. Pre-selection aperture uncomfortable.
Build quality: ★★★★★
Metal, as everything should be.
Market value / value of subjective: ★★★☆☆
Less than $ 150 is a very good price.
Here are some sample pictures.
They were made with Sony Alpha 300.
Pictures were taken with aperture F/4 ISO-100
All photos without amendment in graphics programs.