If you can get your sons to post a high-resolution, colour scan (ie: 600dpi or greater) of the area I am pointing to in my attached picture, it will help identify your BPN.
Even if it cannot be easily seen in the scan, I can do a bit of Photoshop magic to make it appear.

Logged
BWJM
Member of CPMS, RCNA, ONA, ANA, IBNS, WCS.
Treasurer, Waterloo Coin Society.
Show Chair, Cambridge Coin Show.
Fellow of the Ontario Numismatic Association.