panzervii

To add to the mystery, I saw another pretty good-looking U-Boat badge at the recent "Show of Shows' militaria show in Louisville, Kentucky, USA, that also had a 5-in-box stamped on the reverse. However, the other badge had a larger numeral and the "box" was open at the four corners. The vendor admitted the badge was "controversial" for having the mark.

Please give me your assessment of this U-Boat Badge. It is stamped zinc with a narrow tapered non-magnetic pin. The thick wire catch is soldered to a pedestal platform. There is what appears to be a small italic numeral "5" in a square on the reverse. I'm having difficulty posting images directly, but a member has been kind enough to offer to post them for me. Please be patient until they appear. Thank you for any opinions on this piece!