The second offering by the company http://www.xtz.com¹, these Herbal Energy Mints were available back around Y2K, most prominently from ThinkGeek when it was just getting into caffeine-chic. Their main draw are the three G's: Guarana, Ginkgo Biloba and Ginseng, and that they were sugarless. Between what is in the guarana and what they add in, there is almost 3mg of caffeine per mint. 75 per tin (5cm x 3cm, rounded corners), all mints have Peppermint, Spearmint, Wintergreen flavorings in them.
I seem to recall the ThinkGeek adcopy reading something along the lines of "they're the size of a dialated pupil", which evidently was about 3mm in diameter, 1.5mm thick (about the size of an Advil).
Natural and Artificial Flavors
² blatantly stolen from http://www.svc.com/xtz-mint.html