I have these Poland gros coins and have a few questions about them:
Coin 1


This one looks very odd. It looks like the metal peeled off. Is it a fake? The surface looks like silver, but I don't know about the interior.The legend and year are not entirely readable.
Coin 2


1598 3 gros
Legend:
av: SIG III D G (REX PO?) M D L
rv: GROS ARG TRI R PO 98 B
Is the B in the legend a mintmark? Shouldn't this coin be silver?
Coin 3


1599 3 gros
Legend:
av: SIG III D G (REX PO?) M D L
rv: GROS ARG TR R POLO ? 99 E
Is the E in the legend a mintmark?
Coin 4


This one is easy:
1593 3 gros
Legend:
av: SIG 3 D G REX PO M D L (Sigismund 3 Dei Gratiae Rex Poloniae Magni Dux Litvaniae)
rv: GROS ARG TRIP REG POLONI 93 I F (don't know what it means exactly)
This one looks ok, I got it as a present, I don't think it's a counterfake. I'm not very good at grading (could it be xf?, it looks cleaned to me). These coins circulated in Roania too, so here they are quite frequent. I saw similar ones for up to 150-200$. I think there's a little die crack on the obverse between the X-PO-M.