I am looking at two very similar C.T. plates with the image of Queen/Princess Louise which are listed on eBay. They are not identical and have different identification on the verso. The links are:

http://www.ebay.com/itm/400677768832?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

and

http://www.ebay.com/itm/161252240271?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

Along the outside border there are marks which look like arrows. The number and position of these are different between the two plates.

I would appreciate it if someone would please respond with what significance these arrows and their number and position have.