Are they supposed to have serial numbers on the back of the PN? Whether yes or no, for both the first and second release? Mine is a second release bought from Japan and has serial number on the back of the neck. A friend's i-33 is the first release bought from someone on this forum and does NOT have serial on the back of the PN. Helping to verify as I've noticed on some sites the First release looking "i-33s" are selling at less than US$100. Thanks in advance.