Auctioneers and venues selling at top levels have to maintain high-standards to consistently draw a serious collectors wanting the unique items they have.
Obviously not all items can meet those standards.
However, if you browse photos of the items they want, you may noticed that not everything needs to be in pristine condition to fetch a high price. In fact, many times they're not.
Items that sell best, generally have some combination of historical and/or cultural significance. Combined with rarity and a very competitive collector base driving prices high.
Free price research and online appraisals, offered by most top auctioneers, through their websites or inhouse specialist. Can be a way to find if your item meets their standards.
However, if after substantial research you find your item doesn't meet a top-tier auctioneers standards. Don't give up. Because your item may still hold a high value to local or regional collectors and buyers, through a local auctioneer.
Many shops offer lessformal ball-park appraisal process. Often conducted by email through an exchange of photos and information.
If you don't see free appraisals offered on their website, email-them, with your version of the following (feel-free to copy, paste and modify):
I have a [write a brief description of your item] I'm considering selling, and was wondering if you may be interested in selling it in your shop as a consignment?
If you're interested. Would you please send me information detailing your resale fees and/or commissions. Along with your best free ball-park-estimate for its resale value.
If you need any additional information or photos, please let me know how I can help. By contacting me at: (write your preferred contact method).
Thank you for your time.
If they won't do a free ball-park-appraisal, move-on to another auctioneer, shop or gallery who will. Ideally you want several estimates, to make sure they're all in the ballpark.
Free Online Appraisals, by Top Auctioneers
If you've done a little preliminary price research, and think you may have found something rare. Most auctioneers offer free online appraisals which can help you confirm it.
Getting free online appraisals from several auctioneers, allows you to compare estimates and selling fees before committing to a consignment agreement.
If they think you found an ultra-rare-treasure, don't be surprised if they offer to come take a closer look on the next available flight. Auctioneers have been known to occasionally do this, to get a jump on their competition.