Many home hobbyists, including me, buy coins online from auction portals like eBay, Proxibid and iCollector, to name a few. A “portal,” in and of itself, is not an online auction. Rather, it provides a uniform digital platform through which dozens if not hundreds of small auctions, timed or live, are occurring at any given time on any given day.

Unlike sessions on portals, major auction companies usually offer only holdered coins from top grading companies. Hobbyists with little numismatic knowledge can bid with confidence, certain to get an authentic coin, usually at a reasonable price.

Auctions on portals offer slabbed coins, too, not only from those top companies but also from bottom-tier ones that grade every coin — even ones damaged, polished or altered — as high Mint State.

To bid successfully here, buyers must know numismatics, or else they risk losing hundreds of dollars on inferior coins, including counterfeits.

So why do hobbyists, including me, bid on portals? You can find magnificent coins at below-wholesale prices that have lain dormant in bank boxes for a half century.

Don’t register and bid via a portal unless you trust the particular auctioneer. Some are hosted by reputable dealers and auctioneers with fine reputations and numismatic expertise who treat buyers with the same courtesy as onsite clientele.

Auctions hosted by reputable dealers and auctioneers will be easy to spot. They have sharp photography, low buyer’s fees, choice consignments and quick, inexpensive shipping. They use PayPal or Auction Payment Network to process credit cards.

Avoid those that have high buyer’s fees (some charge as much as 22 percent). Others may require you to contact them or a third-party shipper with your credit card information — perhaps the biggest risk of all. You never know who has access to your financial data.

Always read terms of service for each estate auction or online session. Many do not allow returns for any reason.

Be sure you know how to operate bidder windows if you join a live auction. Portals typically have training videos.

Never bid on a coin unless you can reasonably assess its grade, variety or condition. Otherwise you’re sure to experience buyer’s remorse.

Check Coin World’s Coin Values to know latest values (and always figure the buyer’s fee and shipping into your maximum bids).

Michael Bugeja, a coin collector since childhood, is a professor at Iowa State University and also a member of the Citizens Coinage Advisory Committee. He is a nationally known author, journalist and educator.