User Agent String.Com 

User Agent String explained :

Mozilla 1.2.1
Mozilla	Name : Mozilla
5.0	Mozilla version
X11	X Window System a windowing system for bitmap displays
U	Security values: N for no security U for strong security I for weak security
AIX 0043031B4C00	Operating System: AIX Version 0043031B4C00 (Advanced Interactive eXecutive) UNIX based operating system developed by IBM
en-US	Language Tag, indicates the language for which the client had been localized (e.g. menus and buttons in the user interface) en-US = English - United States
rv:1.2.1	CVS Branch Tag The version of Gecko being used in the browser For the Mozilla browser this is the browser version as well
Gecko	Gecko engine inside
20021209	Build Date: the date the browser was built
Last visit:	2018.07.28 01:46
All Mozilla user agent strings