Not many differences as far as i have tested the new 31 (silver) against the old MYJ (black)
1- Lens Pouch : actually the old "31 / 1:1.8" inscripted pouch might have already been replaced by the new one before the HD coating with Vietnam production :
2- Barrel's inscriptions : the "AL" is now lacking :
3- Lens-cap inscriptions have been enhanced :
4- New HD coatings (on both sides of the lens) are a bit more greenish than the SMC ones that have purple reflections :
5- The aperture blades have been slightly elongated and curved :
I am trying hard to detect any results rendering differences on the samples that i can shoot under today's all grey weather (with K-1), first comparisons don't show any difference :
- on bokeh
- on CAs
I will hopefully try "starblitz" shooting tomorrrow..