Is there a noun form of the word "archaic"? The closest word I can think of is "old-fashionedness" but it seems rather clumsy.
There are two uses of the word novelty. One is for an intangible characteristic of something, and the other is for the thing itself. Your suggested answer of "old-fashiondness" suggests you're thinking of the first usage.
In that case, I'd suggest quaintness. From dictionary.com we have
with quaintness as a derived form.
However, I believe that UK and American usage of quaint may be different. I'm answering from an American perspective.