Inscriptions on Valli

[Gallus Marinus Micarius]

I noticed in Bishop's Roman Military Equipment that the Valli pictured on page 103 (first edition) or called "chevaux-de-frise" had a centurial inscription on it. Does anyone know if these were burnt in or carved? And how common are valli finds with centurial inscriptions on them? I'm guessing that it was bad legion juju to "borrow" a different century's valli when tearing down a fortification...."oops frater, is this yours?!? oh, my mistake entirely..." ;-D