The module I use almost always is the fabulous Optomix. I have silver panel and black panel Models.
I heard that the older Modules used ""better Excelitas Vactrols but there is no info visible on the Vactrols.

They differ in the following items:
- The Black panels have the Vactrols stacked on a separate layer, the silver Optomix models have the Vactrols integrated directly behind the panel.
- The sound is also different. Most obvious is that the black optomix does a Bassdrum when with a strike input and no input. The silver panel remains silent.

Does anybody know which version is V2 and if there are any other important differences?