Same guitar, the Mosrite Celebrity I?
Jay, I believe the photo you posted was of Glen rehearsing for San Antonio's Hemis Fair theater apparently on or around August 1, 1968. The photographer was Ralph Crane.
Hemis Fair (aka HemisFair '68) was the official 1968 World's Fair (or International Exposition) held in San Antonio, Texas, from April 6 through October 6, 1968.
Crane also took this photo (below) of Glen's performance at HemisFair in August 1968.
Source: http://images.google.com/hosted/life/f9 ... bb6de.html
-- for non-professional use.
Various archival sites (e.g., a university in San Antonio, city newspapers) have photos from this landmark fair but are not accessible, at least not that I can find yet.
Potential source: http://www.lib.utexas.edu/taro/utsa/003 ... 00346.html
Perhaps in one of these archives, a better photo of Glen with this guitar--facing the photographer--can be found.