I don't think that's a casting seam. I don't see the typical softness on the devices of a cast coin, and I don't see casting bubbles. Some spots of coppery colored metal might indicate it was overcleaned and/or repatinated at one time, but I can't condemn this coin as a fake based on your pictures.
No, not necessarily. Many ancient coins have beveled flans. That is not a casting seam, and the fabric of that coin looks authentic. You also find this type of edge frequently on Ptolemaic bronzes.
A seam results from making separate molds of the obverse and reverse of a coin and then joining the molds together. It must be difficult to get the two halves to align and fit perfectly so that when the mold is used to cast a coin the joint between the two shows up. The irregularities in the edge of your coin could just be imperfections in the flan used. It does not look like a classic casting seam to me. Black sea area coins are often faked or heavily tooled so I would be careful buying them.
Also, remember that some flans are cast in two-part molds. So, not all coins with casting seams are fakes. More information/knowledge is required .
Good point TIF! Often the casting sprues were left when the coins were struck creating characteristic nubs on the sides of coins. Coins from Syracuse come to mind.
It is indeed a seam, but not from casting an obverse and reverse die. It is a casting seam from the creation of the blank planchet and is a remnant of how it might look prior to striking. Many people are not aware of how blank planchets were made, so a coin like this might confuse them. Seams like this are typical for certain types and nearly invisible (or not present at all after striking) on others. Confusing, I know, but as one gets more familiar you can tell. A good introduction can be found here: https://www.jstor.org/stable/42663813?seq=1#page_scan_tab_contents Though you have to sign up to read it free.
