My 70's vintage blue-line uses glued-on patches of velcro-like plastic fingers-with-balls-on-the-ends to hold the front grille in place. It's possible to pry it loose from the front, but a little tricky to get the prying angle right, because it mounts pretty flush. If I've already got the back panel off, I usually push it from behind with a long screwdriver or a drum stick - making sure I'm pushing the wood frame, and not just the cloth!
'berger XL-2 => EBS HD350 => EBS Neo212
Steinberger Club #0013, Pedulla Club #147, Pre-EB MM Club #44 , Epiphone #90, EBS #34