I am 100% in agreement with the use of the two term interchangably. I offer as the basis for my opinion page one of William Campbell's
Greek and Roman Plated Coins where he refers to
his subject as "the probable method or methods of silver plating as exemplified in
ancient coins - the
fourree or subaerati pieces." For no better reason I spell the word with two R's and two E's just like he did but I'm too lazy to trick my keyboard into accenting the first E so I don't bother with that. I really enjoyed Campbell's book and recommend it to all!
The book concerns itself with what I call the silver foil method
fourrees or, again, what I would call
plated pieces rather than the late
Roman washed items. Neither word has any relationship to whether or not the coins were made officially or not but refers only to the fact that there is a better covering intentionally placed over a more base core. For the purpose of naming it makes no difference who made the things but only how they made them. I also disallow the term being
applied to coins which were 'pickled' in acid to surface enrich the flans before striking. To be
plated, there needed to be a sandwich of dissimilar metals.
A term for the iron core things probably is not common because the coins made and surviving are so
rare. I have seen a couple as opposed to thousands of
fourrees.
Finally, I'll mention that I am unreasonable enough that I irrationally discount the opinions of people who use the term
fourree to refer to
fakes of other styles.
Fourrees may be
fake (or 99% may be
fake - your
choice) but not all
fakes are
fourrees. Using the term in this manner strikes me as a sign of not having done the basic study necessary to understand the question. Call it a pet peeve.
I'll also mention that recent years have really seen an increase in the market
price of
plated denarii. When I developed an interest in them, common ones were worth less than ordinary late
Romans in unsectacular condition. Only
rare types sold well. When we started seeing a lot of the so-called 'Limes'
denarii (not produced by the foil method but another topic altogether) there seemed to be a great increase in dealers willing to sell the things to beginners without full explanation and a subsequent increase in collectors that thought it was normal to find
denarii made of copper. We now need someone to do a proper study on the entire subject of unofficial and
counterfeit ancient coins (solid, barbarous, deceptive, local use and probably a dozen other permutations on the coins not being 'quite right'). There are simply too many of the things to justify the old answer of
writing them off as beneath our interest.