I just got a few more ancient coins and I have no clue what they are, how rare or historically significant they are, or what they are worth. Would love some more info on these. Thanks!!
Here is how you should hold it: Your concave coin is byzantine, and probably this: http://labarum.info/lbr/show.php?coin=20030
The bottom left coin looks like a tetradrachm of Claudius II from Alexandria. Here is mine but with the eagle head left.
The coin in the middle of the top row appears to be a nummis of Constantius Gallus, possibly minted in Nicomedia. It dates from 351-354 A,D, The reverse depicts a solder spearing a fallen enemy horseman. It is a very common type.
Funny enough I recently had some CT help identifying what I think is the same type as your bottom middle coin: INDO-SKYTHIANS. Azes. Circa 58-12 BC. Æ (29mm, 13.52 g, 12h). King right on horseback / Zebu standing right, grazing; a in Kharosthi and monogram above. Senior 91.2; BN –; HGC 12, 656. VF, rough green surfaces. Rare.
The dumpy, thick one on the bottom right is a dump from India, probably, probably Mughal. If it weighs around 20 grams you can do a Google image search "Mughal dam" and see how hard it is to figure these out, if you can't read the writing. Many seem to be from around the time of Akbar the Great (16th-17th C. AD), but these were made for centuries. You might post that one on the World Coins forum for more useful information than I can provide. There are some very serious Indian collectors on other forums that could help too. That being said, I have a few of them and I really enjoy them. Massive, yet small, complex but beautiful. Sorry to say they don't seem to be worth much - I've actually found some in my local dealer's junk box. A "Mughal dam" search on eBay will pull up scads of them (mostly from sellers in India). But maybe yours is a rare type? I just don't know. Nice batch of coins.