Always Authenticate
Your biggest concern when shopping pre-owned is probably whether or not an item on your wishlist is authentic, and understandably so. The good news is that most reputable resale marketplaces have a policy in place to guarantee the authenticity of their inventory, whether that means authenticating every item in-house or refunding you in the event that your purchase is deemed inauthentic by a third-party professional.
Tradesy uses software technology to automatically identify and remove inauthentic items from its platform, with a 99.7 percent accuracy rate. Vestiaire Collective ships each item to its corporate office where it is first authenticated in-house and then sent to you (it should be noted that there is an additional fee for this). All items over $500 purchased from Poshmark are first shipped to its headquarters by the seller for authentication.
While I take comfort in money-back guarantees, I always do my best to ensure that I'm not purchasing a replica to begin with (TBH, it's just not worth the hassle). I spent years manageing a local-owned designer handbag resale shop where confirming the authenticity of an item before passing it off to a third-party was quite literally my job. I learned during that time the importance of being able to spot poor quality versus superb quality, which you could just as well learn from studying pieces already in your closet, or combing designer collections online and familiarizing yourself with the structure of each piece.
While quality can be hard to judge from a photo, blatant giveaways of replica handbags are often poor stitching, incorrect logo fonts or sizes, incorrect interior fabrics, and incorrect or the altogether absence of serial numbers and date codes. It's important to note, however, that the presence of a date code or a serial number doesn't exactly guarantee authenticity either. Often, these numbers have formulas that replica manufacturers have either failed to replicate properly or were thorough enough to replicate to a tee, so the aforementioned factors are just as important. When in doubt, consult handbag review sites like PurseBlog that are dedicated to dissecting the nitty-gritty of designer logos and identification codes.
I'm also a strong advocate for authenticating my purchases through a third-party service (I swear by Authenticate First), regardless of whether or not I'm suspicious of an item's authenticity. Chalk it up to bad experiences with eBay and Etsy, but IMHO the extra $15 is worth the peace of mind. Plus, I've lost far more money in the past from return fees when shipping back replica items.