You have to read the eBay descriptions
very carefully, & send the seller questions when in doubt. After a while I started recognizing some of the careful wording some sellers use. This morning I was reading a description that said the saw "turns." Doesn't say anything about the saw having compression. A lot of them rant & rave about an item, but actually give you very little useful information (like a used car saleman). One day auctions are a red flag. Poor quality photos are a red flag, but to be fair some folks have to make do with lousy cameras, & aren't good photographers.
Do a search here at AS using eBay; you'll find all kinds of stories, good & bad. I haven't given up on eBay, but I do research things pretty thoroughly before taking the plunge.