I, too, bought multiple blister packs of this. I have an overabundance of centurions, but I wanted the soldiers with the green shields.
One thing I don't particularly care for about the green shielded soldiers is that the shields are made to be held by the right hand only which forces the weapon hand to be the left. Now, I'm no expert in ancient Roman history, but it seems to me that the dominant hand should be the one that holds the weapon and since most people are right-handed, I think that Playmobil erred in this.
But what do I know? Maybe the Roman army gave all their lefties green shields.
As Gepetto says, we've had quite a discussion over this shield and it's apparent wrong-handedness.
My conclusion is that the original shield (I think it first appeared in Set 3651, thanks Playmodb) was designed as a Pavise or wall shield, the sort of static shield a crossbowman would carry to within bow range of a castle walls during a siege, then shelter behind while preparing his shot, and expose his head & shoulders over the top of while shooting.
The klicky should carry the pavise within crossbow range of the target, put it down and shield behind it, while getting his bowshot ready. A Pavise was large and heavy, so it is reasonable that the handhold was on the dominant side.
For this purpose it's ideal, but even the person setting up the packshot was confused by the handhold, and put the shield in the klicky's right hand and crossbow awkwardly in his left, maybe because the figure designer had give the klicky an eyepatch. It's been causing confusion ever since.
The pavise shield is still used correctly for crossbowmen, the most recent use in set 4808 of the Wolf Knight collection, though this klicky has a short bow (oops Playmobil).
In the case of this blister pack, originally Specials 4560 & 4632, Playmobil were really just testing the water for the potential interest in a Roman theme and nothing was quite right, they were just using existing pieces to create something like a legionary. This shield was the closest they had to the classic Roman shield.
Here's the use I put these blister figures to: