FWIW, My '77 Series I came with what I assume were original, regular brass(ish) strap buttons in the case, but the bass actually had these weird cylindrical buttons afixed to the body. These buttons weren't designed to be used with a regular strap, and had a locking mechanism similar to the Dunlop design, but I don't think they were Dunlops.
Some years later, I installed the best available locking system, which at that time was the Schaller.
Some more years later I realized that nearly all my basses, except my Alembic, had the Dunlop Dual-Designs, so I caved and installed the Dunlop Dual Designs. At this point I've probably clocked more stage/performance time with the Dunlop Dual Design than any other locking system.
As substantial as Alembics are, I definitely recommend strap-locks. The long, meandering tale above is just to illustrate that after a few side-trips, I wound up doing what you intend with your newly acquired Alembic i.e. installing Dunlops.
