All Nylon 66s, the Brazilian copies of the Nylon 66, and the Nylon 76 had the Spencer-like tubular magazine in the butt.

All Nylon 77s and 10Cs had detachable "clip" magazines.

All Nylon 10s were single shot, all Nylon 11s had detachable "clip" magazines, and all Nylon 12s had under-the-barrel tubular magazines.

IIRC.