Damned columns (and sculptors)!
One does never know how much he can trust them... As soon as you take for likely the presence of two different kind of shields in the same unit or army for different needs, then you also see (as below) soldiers with different shields, same armour, but the ones with oval shields have the gladius on the right while those with the squared shields have the gladius on the left...
Anyway, not always! For example, these two auxilia below, both with oval shields, have the gladius on the left and on the right, though I don't think that one is a centurion...
What about the good old way of the official (not provincial) roman artists (or better, that worked in Roma) that were always interested (or expected) more to the symbolism than to the accuracy?
Anyway I agree about the different weapons/different needs theory: it makes sense. Moreover the oval one can be well packed in the squared one. If so, how has to be the leather covering, have we to consider two leather covering or one for both? If I remember findings are for the first one, but any finding about a covering having room for both the shields exists?
Just I like to know how long the train was long in campaign, and how I asked in another forgotten topic, how much iron, wood, leather, bronze, lead, paint, servants, animals, etc., needed to keep a legion fully operating. Duplicating weapons adds lenght to the train...
Valete,