I have already established year of issue for almost all crown caps issued in Serbia in 21. century. This research has been done by pairing dated bottle labels and their graphical design with the design on the cap. Auxiliary help was found on breweries' official Jutube channels since introduction of every new product / type of a beer was followed by dated video clip. When both of those were not available, I was turning to dated news articles on the web. Today I discovered that additional, and sometimes superior method is using factory signs (FS) that appear on the skirt of a cap. This led to even finer dating of several caps, and establishing variations of the same cap produced at the beginning, middle and at the end of its run.

Major inspiration for this investigation is encountering collector's web site of Davide Mascherini (CC.I #11), one of the founders of the main crown cap catalogue http://crowncaps.info/. His web site is located at http://davidecaps.altervista.org/, and here is how majority of his web page for Serbia looks like:
 

In addition to pairing of previous research with this new method of dating, I have gone through hundreds and hundreds of copies of Jelen caps from 2007. till 2015. (while the deer was on the cap), and findings were consistent with results in above table. The only thing that Dave missed due to his limited number of samples (maybe just one of each) is GG sign on caps of Jelen on white bacground that were in use until 2009, when the cap with gold background replaced it. In my stack of the white caps I found all 3 signs: the oldest one from 2006. as one piece I purchased on eBay, tens of those from 2007 (GM sign), and hundreds later ones (GG sign). To establish how long was GG version used in deer on gold background, I compared numbers of those to numbers of caps with "tik" sign, and it turned out that the ratio was 5:1, which proves that GG was used for 5 year, and "tik" for only one. The use of the "tik" sign was dated since Weifert cap was certain to be from 2015. and "SAKUPI BODOVE" Jelen givaway is know to have occured in the second half of 2014. GMP started appearing on first Jelen caps after the deer disapeared from it (FILTRIRANO and SVETLO PIVO), and that is in 2016. Similar inquiries into Lav brand and its caps also confirmed the above table which shows dating of FS used on Serbian crown caps in the 21. century. Caps known to be from the 20. century had "mp" and MP signs.

The cosequence of this research on my collection is that now I have, instead of a single cap, 3 caps of a deer on white background, and 2 on gold background that look identical, but differ in FS, and therefore the year or period of use: for white background I have "n" and GM used in 2006. and 2007, and GG used thereafter, for gold I have GG used from 2009, and "tik" used in the last year of cap's production. The table was also confirmed on Jelen with a ball on white background cap, which exist in 2006. version without the year on the cap, and 2007. version with the year on the cap's face. As expected, older one had "n" sign, newer one GM.