questions about cavalry shoulder doublings

[Peroni]

The plate you posted is from the late second/third century and would have been fitted to a lamellar or locking scale cuirass. These had 'keyhole' fasteners. It's shape would be similar to this..

http://www.aeroartinc.com/aapub/rp07.asp


For an earlier reconstruction have a look at Marcus Junkelmann's site..
http://www.klassphil.uni-muenchen.de/~s ... elmann.htm