90% of my UR18650F's have green isolator rings...
I've also got two different wrap colours... older cells are red whereas the newer cells are slightly pinker..
Infront of me I have
UR18650F R1112 - Red/Green
UR18650F M50A - Red/Cyan
UR18650F T27C - PinkyRed/Green
Hope this helps...
These came out of an old IBM laptop pack. (IBM 02K6822)
I cant find anything on them but I'll take a guess at 2200mah and 3.7V Nominal :-D
Id also guess 2009 (from the WT081109)
I've included a shot of the base as well as it isn't flat like others...