For sure, it is a .450 BPE gun, and not a NE full load.
"B.Plomb" means "lead bullet" which indicates the former.
"B. Blindee" i.e. "jacketed bullet" would be required for the latter.

Don't shoot a full load in that double. At the least you'll have a very sore shoulder. In the worst case, you'll have gun and body parts laying around.

Best regards,
WC-