Z2 on an Unmarked Wagner?

Could anyone tell me what the significance is, if any, of the 'Z2' mark on a 10 1/2 inch unmarked Wagner skillet?

Just a pattern identifier. More letters of the alphabet used indicated the need for many patterns for a high volume piece. An additional letter or number might indicate more than 27 working patterns were required.

See also: http://www.castironcollector.com/numbers.php