From Father Z's wonderful blog.
Note both the men in the left and right are wearing vestments that both resemble a dalmatic.
Tunicles are reserved for the Sub-deacon in the EF Mass. Sub-deacons are either a priest, deacon (transitional or permanent) or an instituted acolyte.
So in this photo which shows the two men wearing which look like both are dalmatics, how can you tell which is the deacon and sub-deacon, basing on the rubrics of the 1962 Missal.
Post your answers.