One chip like these four below is listed in Antique Chip Guide as Initial Engraved Diamond PO-EJ. The chip in Bob's guide is the maroon one. Are these others variations of that numbering system, and do they get another identifier added to the PO-EJ designation? Also, does the Diamond refer to the manufacturer? And finally, is there an estimate about the age of these chips? Any help greatly appreciated. Bob if you need the scans to update your antique guide, you have my permission to use them.