Something we use to some extent with the "Allied" marker brought to the fore in the Gulf conflict with V's of varying oriantations and other markings etc to denote formations/SQN/Command etc It was used to clearly identify friendly forces, If you knew what you were looking for you could tell exactly what unit it was. However it has been for the most part made obsolete with the introduction of the Combat Identification Panel. The Markings alongside Callsigns are still to some degree still used on our vehicles.An area I've limited knowledge of but in a previous job I worked alongside the armed forces a bit (field testing products) and for exercises, etc. a marking like this would sometimes be used to tag those acting as the opposing force.