Preparing to renovate the charging system on my ’84 R100RS, I assumed that the bike had an electronic voltage regulator because of the year it was built. The metal case however led me to mistakenly think I had a mechanical voltage regulator.  I learned that early electronic voltage regulators had metal cases like the mechanical versions – just with a somewhat shorter metal case.
Opening the metal case (by simply removing the red tape) I confirmed having an electronic voltage regulator.
Notice that this model has a small potentiometer – presumably that controls the output voltage. It’s marked with a white paint stripe to show its set to the factor setting.
A new OEM electronic version: