I have a #11 Griswold skillet similar to the one on page 20 of the Blue Book but markings are a little different.  There is  no "Cast Iron Skillet" across the top. Below the Logo it only says Erie  (no Ohio, U.S.A.).  It looks like the #8 on page 21 but does not have the quotation marks around "ERIE".  My question is, is it common to have variations on the markings?  This was a freebie piece in poor condition.  Setting upright in a leaking barn full of water, bad pitting on the bottom of cooking surface, so not a collector.  I love using Cast Iron to cook but am a preschooler on collectables,  just got Blue and Red Books from Greg yesterday.
Thanks, Mike