"Can't see a mark on it;" that's pretty slick.
My wife works with photographers, and they keep up with the market for their gadgets. Most seem to agree that Ebay is not a great place to buy gear.
It's very important to list in the right category. If I'm looking for something, I search from the front page and follow the links to the best matching categories. The best deals come with items improperly labeled or inadequately described, good for buyers = bad for sellers.
My five cents: Clear photos are indispensable, so take special care with backgrounds and views. If your selling technical equipment, post schematics and specs, or provide a direct link to that info. Also, be absolutely honest & courteous. Hand out positive ratings whenever you can. Courtesy is reciprocated. Package items carefully and ship promptly. Don't gouge with handling fees.
Yep. Honesty is best. I have one auction running right now that in the description is "Looks like the dog ate it" .... It has 3 bids. LOL!