Hi Debra, I know your message is quite old and you probably already know this - but in the Prossekel church records the name was spelled Koplin / Koplien... and there are quite a few families with this last name in Wisconsin that I'm aware of. It was actually fairly prevalent in that area called the Netzekreis which included parts of the Prussian counties (Kreis Filehne, Posen; Kreis Czarnikau, Posen; and Kreis Deutsch Krone, West Prussia).

The records from this area are microfilmed by the LDS Church (Mormons) and available to view. Some of them are online from the Polish archives as well, and the Mormons are working to get them all online in time.

I have some of the Prossekel records copied - not all - happy to check info for you if you want.