Full Idea
If we count the concept 'coin in this box', we could regard coin as the 'unit', while taking 'in this box' to limit the scope. Counting coins in two boxes would be not a difference in unit (kind of object), but in scope.
Gist of Idea
Counting 'coin in this box' may have coin as the unit, with 'in this box' merely as the scope
Source
M.R. Ayers (Individuals without Sortals [1974], 'Counting')
Book Reference
-: 'Canadian Journal of Philosophy' [-], p.139
A Reaction
This is a very nice alternative to the Fregean view of counting, depending totally on the concept, and rests more on a natural concept of object. I prefer Ayers. Compare 'count coins till I tell you to stop'.