Vintage Jack Daniels vs. Johnny Walker ad poster

I own a Jack Daniels vs. Johnny Walker at Madison Square Garden ad poster. I've had it for twenty five years and it wasn't new when I acquired it. It measures 28''X41''. It is mounted on a wood-type material and it is printed on both sides. I've done research on the internet and can't find any information about it. I've thought about selling it but I don't know what the value of it is. If anyone could help me, I would greatly appreciate it. Thanks.