Visited yesterday without charging.
The charger is among the parking spots directly attached to the main road.
It seems to be for customers only, but they really went with minimal signage. The only place that mentions customers is the parking meter that says "2 Stunden = Gratis" and underneath "für Gäste Hermitage". Yet at the same time the charging spots are not numbered, so it seems like they are not covered by the parking meter.
On Chargemap there have been comments in the past saying it's for customer only, but I don't know what their source were.
Hermitage have their logo on the charger but otherwise it's regular MOVE signage. It's cool to see the charger painted black, that's not a common sight.