The present invention provides a counter (203) comprising: a first ring member (201) having first indicia and a second ring member (202) having second indicia, each of said first and second ring members being rotatable in increments about a common axis, one or both of said first and second indicia indicating a count； and a drive mechanism (205) for rotating said first ring member and for rotating the second ring member after one or more predetermined degrees of rotation of the first ring member, wherein said drive mechanism comprises a pawl-and-teeth mechanism which comprises a first and second pawl (208) engageable with a plurality of teeth, and wherein each of said first and second pawls comprise a driving engagement face for engaging in a driving engagement with one of said plurality of teeth, and a sliding engagement face for sliding over one of said plurality of teeth.
