Since the piece is apparently only stamped or carved on one side with no details on the other side, other than possible leftover Lead or other type of solder to hold it to something, I am going to agree with Mackaydon and also say that it is a Seal. The information of the little envelope may actually be correct for the item. I am not sure that the translation is correct but Zegar is Polish/German for timepiece or time period, Cat L/11 may possibly indicate Circa 50+2 (Year 52) or the Year 1150 depending on how you read it, not sure of the MM but I believe that it indicates it was found by U. Gundlach on July 10th, 1969.
Frank