Hi,
Concerning the authenticity of the cap I would try the following forums:
www.wehrmacht-awards.com
http://gmic.co.uk/index.php?
You register yourself and wait for the authorization to join both forums but there are some very nice experts on them.
About the historical information, mainly conected to the alleged generalīs captured, I would recomend the following:
http://forum.axishistory.com
Good luck,
Douglas.