If you're selling harmonicas often, you probably don't need this information, but many people sell one just once in a while, so I'm aiming this guide at them. First, be sure whether you're selling an antique, vintage or newer used harmonica. Unlike many products, harmonicas don't have dates on them that can be used to determine what year it was made. On the back, there are many dates, but those represent dates that awards were garnered, or some other meaning, but not when it was manufactured. What will date it  (ballpark) is if , on the back, it has a small star, usually six points, in the middle of the center circle, being held with hands. That puts them before WWII. I've been told the star was removed because of Hitler ordering it. I've also been told that the star actually represented Hohner's six children, not a reference to Jews. That makes sense to me, as I also have one harmonica with five points on the star, which could be before the six pointed ones. Some have large stars in the circle, some have small stars, and I haven't figured that out yet, but I'm still researching it.And, they're not handmade, as I've seen in several auctions. They were handmade (at least by Hohner) around the 1850's - 60's, when he sent some over to the US to have a relative promote them. Those would definitely be "antique", and worth quite a bit of money, but I've never seen one, so I don't know what they look like. The ones with a star on the back (Hohner only) could, by some, be considered "antique" also. Ones manufactured after WWII would be closer to be called "vintage". I corrected someone recently, when they stated that their  Hohner Marine Band was made in 1881, when, in fact, it was without the star and in a plastic case, which puts it closer to 1981, and they got angry with me. Imagine how angry they would have been if they actually sold it! And their starting price was $50, which put them out of the selling ballpark. Knowing - at least a little, of when the harmonica was made gives you a better idea what to ask for it. Other harmonicas that are not made by Hohner are even harder to determine the age, so be careful what you're advertising - when in doubt, state that on your auction - say when you THINK it was made, but leave it wide open for the buyer to decide. Taking photos of harmonicas are difficult, due to the fine details, but try to not load a photo if it's not clear. I have found that my photos are fuzzy , usually because I've moved when snapping it. With digital photos, I can erase them easily, so I take a bunch of  photos from different distances, angles, etc., then sort out what I want. There are different kinds of folks buying harmonicas, usually those looking for vintage ones to add to their  collection, and those looking for ones to actually  play. I have two sets, myself, and  never  mix them. Always note on your auction what key the harmonica is - it's usually a letter by itself at the end of the metal portion, but I've seen it in many places.The last thing I want to suggest when auctioning harmonicas - or anything - is research it, by looking at what is out there already. See the opening bid, see the response from buyers, and see what it finally sells for, and you'll have a better time getting the most for your item, and your buyer will give you a positive feedback when they feel you auctioned it with honesty. Have fun!