Nice find a figure 8, ball made some really crude stuff. Here is a link to someone who just got back from the munci jar show and picked up one just like yours.
http://balljarcollectorscommunitycenter.yuku.com/topic/3507
No idea of value other than engraving errors are worth a small premium over jar value to me, There are just so many mold variations of the 3 L balls that to try and collect them all is well nigh impossible but this one is neat.