In Wagner terms, this would be a version of their popover pan, slightly different than their "S" muffin pan. It would have to be after 1957, as it is actually made using a modified pattern of a Griswold #10/949, which dates from the 1950s. In the case of this unmarked one, the A would just be a pattern identifier. Most likely it was sold in a Wagner box or cardboard sleeve. These are also seen marked (badly) Wagner Ware stylized logo (no Sidney -O-) Made In USA.