Not my area so I'm going based on a quick search and am happy to be corrected by someone more knowledgeable in the field, but looking at this article it says >"Peter Pentz forklarer, at der kendes omtrent 1000 af de små torshammere fra vikingetiden

rough and quick translation:

>Peter Pentz explains that there are around 1000 known examples of the small (amulet) Thor's hammers from the Viking Ages.

And while I imagine he was pulling a number from estimation rather than something precise, that does seem fairly small for a time period with such association with this, and if that number is correct it is a pretty awesome find to build the collection