Szeląg koronny 1661. Has reverse on both sides. What type is it?

I just found this 1661 szeląg koronny. The lettering is: "SOLID R(?) REX (T.L.B.)? 1661". It has reverse on both sides. Is this a common error for those times? I've searched and couldn't find anything on the internet.

woow, very nice!
It is propably a contemporary fake.
Tytus Liwiusz Boratini was very good in filling his pockets with these coins (boratynka)...
https://pl.wikipedia.org/wiki/Tytus_Liwiusz_Burattini


Perhaps you can contact this member:
https://en.numista.com/echanges/profil.php?id=62681

Nothing special, common doubled die only . Compare: https://e-numizmatyka.pl/phpBB2/viewtopic.php?t=29806&sid=6fd0b3a26068501a1c999b7421072e78 or http://myvimu.com/exhibit/2850917-podwojne-bicie-boratynki or https://www.olx.pl/oferta/boratynka-16-destrukt-podwojne-bicie-stempla-CID767-ID9LqEW.html