I had to smile when I passed the Quayside former CUSTOM HOUSE to see that the brass plate for the present residents shows CUSTOMS HOUSE, yes with an S. So I'm not the only one who gets the name wrong but I do accept that it shouldn't have a S
I cannot remember what that brass plate (that is there at the front door of 39 Quayside now) actually says, though I have seen it.
If they are using the name as part of their 'name plate' (which would surprise me, as I thought they were calling 39 Quayside Trinity Chambers now) then they would be correct to add an "s" (or anything else they want) as they cannot legally call it Custom House - because it isn't one.
That is the same reason the theatre in South Shields is called what it is.
If the brass plate (you saw) is only 'referring to' the former use of the building, then I am surprised they got it wrong, as when they first moved in (in 2004) they put up a brass plaque that got it right!!!
The Journal, November 10th 2004 . .