It's hard to tell from the image you have posted, but if that's not a crop this is quite likely reticulation. This is something that happens when your temperature control during processing is poor, and in particular it happens:
if there are large, steep changes in temperature between stages, where 'large' is somewhere above 5°C C (5 is pretty safe, 10 ...
If I had to guess, I would say that this image was underexposed and then corrected for (perhaps unwittingly) when scanning.
Two reasons for this guess:
You mention you metered using the camera's built in reflective meter. I believe the FM2 uses centre weighing for its metering. That means that it determines the exposure mainly on the light in the centre of ...
For highly specular surfaces with scratches on, setting up a scene where the direct reflection off the specular surface is as dark as possible, then lighting the surface such that the scratches are highlighted by the light source should be key here.
The trick will be finding a light source direction, and size of light source that highlights the scratches ...
Given the average luminance value of each frame L1 and L2, you can calculate the ratio of the exposure values EV1 and EV2 as
EV1/EV2 = log2(L1)/log2(L2)
And see Wikipedia for more details on this formulation.