This advice is "on-the-money". For my sins, I spent most of the 1990's as a record dealer with a market stall three days a week, and one or two record fairs at the weekend.
If the answer to "has anyone looked through this collection before?" was Yes I usually walked at that point. If I was the first to look at a collection I would make what I considered a generous instant cash offer for everything, after cautioning would-be sellers that the vast majority of LP's are essentially worthless except to the person who is destined to own them next.
SJK's advice above would have got my attention for sure, but IMHO 200 LP's is too few to attract any experienced record dealers.
If I were in the position of the OP I would list them on Discogs first