Shield boss of Junius Dubitatus

[Peroni]

Paulo wrote...

Would a circular boss as the one below be used on a rectangular shield or only on clipeus or flat shields.

Yes, there is evidence that round shield bosses were used on some legionary shields.

Caius Castricius Victor of Legio II Adiutrix (although the stone is dated to the early second century) shows just such a shield. It is hard to see whether the shield was actually meant to be curved or flat though!
:wink:
http://www.romanarmy.com/cms/component/ ... Itemid,94/

there is also this shield boss from an auxiliary cohort of the late first century depicting the personification of Africa wearing an elephant skin headdress. Inscribed: COH I GAE FRVNTONI CVMVNI, "First Cohort of Gaetulorum." This cohort was raised in Africa and was based in Syria from 88 to 91 AD