I found one source (only one!) that uses "Anteds":
But by the time the silver Anteds were issued (in huge numbers), for example, many of the dies are virtually the same, with relatively few die varieties.
Chadburn, Amanda Dorothy Barras (2006) Aspects of the Iron Age coinages of northern East Anglia with especial reference to hoards. PhD thesis, University of Nottingham
That same source also uses "Anted coins":
This is in direct contrast to the Anted coins, some of
which do have an inscription reading ANTEDI (this legend is found on both
the gold and silver coins).
I think that "Anted coins" is your best bet. It's a very uncontroversial pluralization and it's also used in other sources:
As in the case of the Anted coins, the number of dots in the rosette over the horse's back declines.
The Coins of the Iceni
...all unquestionably rulers of western origin, and all issuing coins of the larger module, in the same style as the larger ANTED coins from the same area.
Celtic Ornament in the British Isles Down to A.D. 700
I then noticed the distribution of Dobunni ANTED coins seemed to stretch toward Norfolk and that there was, apparently, another ANTED at the other end of that route.
The Iceni hypothesis — part fourteen
This appears in the series of ANTED coins.
Inscriptions on British Celtic Coins
Nearly all the Ed(n) and Symbols coins appear to be struck from worn dies, whereas the Anted and Ecen coins are fresher, although they too suffer from both circulation wear and die wear to a lesser degree.
A Hoard of Iron Age silver coins from Fring, Norfolk, and some observations on the Icenian coin series