Les Matheson wrote:

Okay, maybe you are right, but we always referred to the slatted Es as 556
birds. I thought the ex Thunderbirds E I flew had a solid slab.

For sure. The old ex-T-bird F-4s were monstrosities of
missing and mis-matched equipment, exempt from many TCTO
upgrades.

And us maintenance pukes called slatted Es as "-556 birds",
too; it was a clearly visible "dividing line" between two
much-different sets of equipment and weapons system operation.