hi @adrianus, as I understood, the consideration was primarily: size. But that has been just an idea. Concrete: many of these pieces (for example this one) were found in Nijmegen in a river-harbour complex,
some in a relatively good condition, in conjunction with large amounts of late Constantini and Valentiniani coins (2nd half 4th century). It seemed improbable to us, such fragile little bronzes would have been in circulation for nearly a century. Two experts (aurelianus and Catuvolcos) stated on this forum, these very small coins even when they are radiate, could be late 4th and 5th century.
As I explained in the
Urbs Roma hybrid thread, I do not completely agree with this analysis, because I think these coins can be late third century pieces ("late radii") that reached (more intensive?) circulation at the point in time that the official coinage approximated these in size. Thanks for your surprized reaction here.
Please enlighten us if you have yet a different opinion on these coins, we found very little references. They are all 6-9 mm, based on either radiate, or much later, example coins.

Lex