How can I determine a fair price on a Granzk ORT, 1618 of Sigismund III? I'm searching vcoins at the moment... Seller says it is a "key date", but I'm not so sure. It has probably been metal detected. Seller is in Europe. He is asking $95 shipped which sounds high.
I have no idea about Polish coins, but that does look in lovely condition. If it were a sixpence or other coin I knew about in similar condition and age I would snap it up. I would caution that it does look in very good condition for a metal detected find.
I found these on vcoins, but they are different dates: for $59.20 this one had sold for $83.73 or so and was XF... This one sold for $36 (but I can't tell when it sold?)
Doug - I think that all those you have pointed at look more like detect finds than the first. They are nice coins though.
According to the 17th century, 3rd edition of the Krause Catalog of World Coins, the 1618 Danzig Ort like this one (either by mint officials' initials SA or SB), is worth $12.50 in VG to $90 in XF. I don't see that this is a key date and, frankly, it looks a little cleaned to me.