They're not wire stabilized. They have inserts in them.
On the underside of the long keys there are the "active" holes where the key stems and springs are located, and the "secondary" holes without springs.
If you have wire stabilizers, then the secondary holes are just blank and empty, and the wires hook into clips and hang down.
If there are no wire stabilizers, the secondary holes have tubular legs hanging down that slide into the stabilizers in the barrels.
You can add barrel inserts and change over to new keys with the legs, but each kind is different and must be accommodated properly.