Hobbies built around systematically acquiring and organizing a set of objects, Robert Stebbins' collector type from the serious-leisure hobbyist typology. Belongs here: coin collecting, stamp collecting, insect collecting, currency bill tracking, velology (the collecting and study of luggage labels), metal detecting as an acquisitive field hobby, and lapidary, folded in here rather than shipped as its own singleton subcategory because lapidary hobbyists most often begin as mineral and rock collectors even though the craft itself is cutting and polishing rather than acquiring. Does not belong here: hobbies that observe or maintain living or natural subjects without acquiring objects, grouped under Nature Observation and Husbandry Hobbies.