Thank you, Lech, for the link, Google translate will help too.
I will read with interest as I was wondering why the so called plumbatae represented on coins look so different from the known object.
(https://www.lateromanbronzecoinforum.com/proxy.php?request=http%3A%2F%2Fjournal.exarc.net%2Ffiles%2Fmain_1.jpg&hash=2463fc79a0e84acd78a3838dd4368d7c3b768c6f)
The little javelin thrown with amentum illustrated on TPZN seems to have also been called verutum and been used by velites.
(https://www.lateromanbronzecoinforum.com/index.php?action=dlattach;topic=1156.0;attach=4490;image)
Some illustrations show velites with two or more veruta held in shield but I have not been able to find an ancient representation and don't know if it is différent from the minor subarmalis that Divusric says (and shows) to be represented on Mainz column.