three cubic acres

[Nils Lid Hjort]

I find it wonderful that Barks chose "three cubic acres" 
to describe the amount of money in Scrooge's bin. Since
`acre' is a two-dimensional measure, of area, it would
follow that the Ducks live in (m^2)^3-space, that is, in 
some six-dimensional space. Makes sense to me. 

One could invite the Duckists on our list to discuss the 
peculiarities and consequences and side effects of life in
six-dimensional space. However, on this occasion I'd be happy
to have your collective expert help to check for me 

. Where was Barks' first use of the "three cubic acres" of money?
. Did he stick to this later on (with reasonable consistency)?
  (I think he did.) 
. I *think* this has been followed up (with _some_ consistency) 
  by Norwegian translations, using "tre kubikkmaal". Where is 
  the first reference to this, in the Norwegian weekly DD & Co? 

Nils Lid Hjort