http://www.keyshistory.org/KL-USGS-NKL-HN-40-1973-Large.jpg
1999 Photo shows more detail:
http://terraserver-usa.com/image.aspx?S=10&T=1&X=2851&Y=13978&Z=17&W=2
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http://ed-thelen.org/loc-f.html#HM-40
http://www.nikeordnance.com/TomCurtis.htm