Well, your cue looks like it is in excellent condition. As an Adam cue from that era, with a very desirable pearl dot and diamond inlay pattern from that period, a six pointer, ebony woods, nice leather wrap, basically almost, if not new condition- I could see an offer of $500 or possibly more.
I wonder if there was a case for the cue, possible that it could have some value as well. Odd to find an unused, solo cue in a closet like that- it was a fairly high end production model back when new. Did the owner have any pool playing history? Most closet queen cues are found in a case in a closet or basement closet where young guys either bought or were given a cue and then shortly went off to college and never returned back to the game.
Some were from guys who went off to the armed services and did not pick up the game upon return. Especially in the late 60s to early 70s when pool halls were closing left and right partially due to the Vietnam war claiming their patrons.
More sadly are the cues that were left in closets from the guys who did not return from wars- Vietnam being the the largest contributor.
Post the case photo if you have one, If the cue is unplayed, and you do want to sell it- I would leave it unplayed so that it can honestly be sold as new old stock- otherwise just enjoy it