Omega Seamaster diver case size question

I am interested in buying a pre owned mid size seamaster diver. Most of them are advertised as 36mm, others as 36.25mm. Is there a difference in case sizes throughout the years? Older, smaller sizes? Or are they all 36.25mm. I know 0.25mm is not the world, but since they are already small, i would prefer the 36.25 😀
Anyone knows? Thanks