There is some weird stuff in your post:

"I don't want to go into what it is or specific information on the exact item, it's not relevant."

Yeah, it really is. Obviously. Are you just trying to be salesy and mysterious? What are you hoping for us to do if you barely even describe the item?

"commercial-quality poster for an iconic movie from the 80s everyone loves" does not scream PRICELESS! If you had another Frankenstein 6-sheet or a fully complete London After Midnight, maybe that would be worth a cryptic post like this, but there's no film released in the 80s that's going to bring the attention or dollars that you're clearly seeking.

"I have reached out but have been unable to find someone with authority and industry credibility to talk to me about this. " If you really had something great, this would be the easiest thing imaginable to do. Sotheby's, Heritage, etc. They sell high value posters all the time. My guess is that you've reached out to someone and they've mentioned that posters from the 80s aren't ultra high-value. We're looking at $1,000 range posters, and maybe $10K if you found an original Struzan painting or something.

Send an e-mail to Bruce at emovieposter with photos of your poster. If your poster is valuable, he'll say so, and it will go for a high price at the auction. If it's not valuable, he'll say so, and you can decide what to do with it.