It looks like my glass/ bottle washer. Is there a knob that turns the hot water on? Mine only had hot water ran the sink until hot set the glass on the wash push the button it would go for 20~ seconds great for rinsing home brew bottles out, those I had to hold the bottle in place because I lost the holder.
I do not think that it is technically a "washer".
It is more for rinsing a glass, by itself it is not enough to wash the glass.
These are used in bars for draft beer. If you rinse a pint/beer glass with cold water just before you fill it with draft beer it will prevent the the beer for foaming to much which will result in to big of a head on the beer.
As a lover of beer, i know this :)
Why you want to rinse your beer glass - "beers pour better in a wet glass"
It would be useful for rinsing any glass prior to its use to insure the dust and stuff that may collect in it is rinsed away before you fill it.
Here is a link to several variants if anyone is curious: