Here's a link to the Polish post office - new stamps this year still use the zloty symbol (it's actually a "zl" with a line through the "l," and not "zt" as I had stated - it kinda looks like a "t" but it's not)

Getting back to the original question, though, I am still not persuaded that the chip is from a genuine casino. At least it does not appear in listings of Polish casinos, such as: http://www.worldcasinodirectory.com/poland/lodz#LIST