Local park....worldly find

So I braved the elements the past weekend and decided to detect in a park used as a local soccer field in the  midst of mid-90 degree heat (not quite so bad as Montana has low humidity - it's a dry hot, like a dry sauna). In a hour and a half, I was able to snag 85 cents in clad along with some pulltabs (you don't know if they aren't gold rings until you dig them) and some random pieces of metal. After coming home, I noticed one "coin" I had gathered had started to leach out its metal inner core pretty bad. The outer portion of the coin was practically unrecognizable so I decided to bathe it in a bit of household vinegar (I know what some of you are thinking, putting a chemical cleaner on an unknown coin. If I was decipher anything out of that mess of a find, I had to chance it and clean it off for better identification).

After cleaning I was surprised to see the following marks. After some research, I discovered I had unearthed  a 1971 German 2 Pfennig coin. Here is a pic of the coin along with what it probably looked like during its better days.