One vote for fakes - they are too darn perfect, somewhat dull, and far too well color matched for comfort.
If they weren't so darn round I would have said dyed freshwater - the color is typical! But as round as they are, I'd say fakes. Vintage fakes? Maybe.... there's nothing to tell their age. Frankly, I am not familiar with vintage gray simulate pearls - the vast majority are cream or white.
The guess may well be wrong - I've given the reasons for it for your consideration.
And here's an example of the artificial color these things remind me of:
LINK.
PS. How do you tell nacre thickness from a picture? I can't... unless it is pealed, or stripes from the nucleus show - i.e. the very worst. And I assume that hammered surface or roundish baroque's might have thicker nacre (think smaller vs. larger . Maxima 'South Sea' pearls)... I cannot see any recognizable features to associate with nacre thickness on these.
PPS. You should see the 'vintage fluff' under my desk, LOL!