First, Sear is a Roman coin expert, not website designer. He is completely legitimate and honest. Not infallible, but as close as they come. I had several of my top coins authenticated. So no worries there.
Second, and this may seem controversial and many of you will disagree. I would never buy a coin in excess of $500 from a private seller unless it had been authenticated. If you have a valuable coin why would you not drop a $100 or less and have it authenticated? Lazy, Indifferent, or perhaps it's a fake? There are options other than Sear but he is rather inexpensive and I think for $200 I had coins valued at over 15k authenticated. When I buy a used car I pay to have the car looked at by a mechanic of my choice, if seller balks I walk. However many people are looking for deals, and steals even. Nine times out of ten they are too good to be true. So with the odds against you why play? Because gambles exist and they usually lose....
In closing, I have only been a collector since September of 2014, yet some great people from this site have aided me and helped immensely. I did not just ask their advice, I took it. Too often we get inquiries about suspicious coins and due to greed our wisest members are ignored. Luckily we don't lose out.
In the beginning I was on
ebay buying, dropped $4800 on fake coins. Luckily I dragged those villains at
ebay to court and won my monies back. Now I only buy from major auction houses, that I can sue, if they throw a fake one my way. I implement my business motto here in the
Coin World. I don't do business with people who I can't sue if they cheat me. Remember that when buying!