Hello! Please have a look on https://www.osm.org/node/12510968508, https://www.osm.org/node/12437856497. You add a tag ref:NMHH to a advertising.
Please have also a look on https://overpass-turbo.eu/s/29AT. The user add a tag ref:HU:NMHH (the values are without a leading prefix NMHH). 
I assume, that you booth means the same reference. If my assumption is correct, can we standardise the two tags to ref:HU:MNHH? 
