research association; research society / group of enthusiasts (as may be found in schools, colleges, etc)

researcher

(education) research project, done by Japanese schoolchildren during summer break, to be presented upon return to school

a laboratory

historic, historical / already-happened, past / former, old, traditional

study of history

historian

oral history

(Internet slang, especially anime and manga fandom) events or things from the past which one wants to whitewash/erase from history (due to it being embarrassing, poorly received, etc.); dark past

historicism