A series is a number of crown caps that are issued at the same time and that are usually on one type of drink in the bottle, eg Carlsberg WK2006.
A set is a collection of crown caps from a brand for different drinks issued simultaneously, eg Looza.
A time series is a collection of crown caps over time, eg Bigfoot, Wernesgrüner.
Click on the left of the country whose series you want to see. If there is more than one series, you will find the overview of that country on the right.