A Couple Of Large Ancient Silver Coins?

Left is Ptolemaic Egypt, one of the earlier Ptolemies.

Right is Seleucus I in the type of Alexander III.

Left one is a bit lightweight, but looks genuine to my eye. I have my doubts about the second (mainly because it's a desired type) but the weight is better--the Attic standard tetradrachm should weigh 17 grams, but standards were sometimes lax, although 15.2g is still on the lower side of tolerable for the early 3rd century BC.