A tegestologist is someone who collects beermats or coasters.

A coaster, drink coaster, beverage coaster, or beermat is an item used to rest beverages upon. Coasters protect the surface of a table or any other surface where the user might place a beverage.

Public houses usually will have beermats spread out across their tables. They are used not just to protect the surface of the table, but, as they are usually made of paper, they can also be used to absorb condensation dripping along the glass or serve as an ad-hoc notepad. Beermats are often branded with trademarks or alcohol advertising. Beermats are not to be confused with bar mats, rectangular pieces of rubber or absorbent material used to protect the countertop and soak up spilled drinks in a bar or pub.

Beermats are usually adorned with a customized image—usually mentioning or advertising a brand of beer, although they can also be used to promote a drinking establishment, sports franchise, businesses or special events.

Some coasters are collectible items. Tegestology is a term coined from Latin (teges, -etis covering, mat) defined as the practice of collecting beermats or coasters, with practitioners known as tegestologists.

More Info: en.wikipedia.org