Spartan shoulder protection

[Giannis K. Hoplite]

If you are referring to the the very early vase depiction of crudely painted hoplites that Paul B. had traced some years ago, i think it is so vague and crude,that we have few chances to ever find out what it means.
In my own guess,it is just the upper part of a supposed tube and yoke,if a bit early.
Khaire
Giannis