Cheyenne #6048D
 
This quad was flown primarily in July and August 1978.  However, 
the Julian days indicate eight lines were flown in September.  The
production log shows the 1978 flying ended in August.  These eight
lines were either given the wrong Julian day or they were flown
in 1977.  The latter is most likely.  As we couldn't be sure, we
labeled all the lines as being flown in 1978. 
 
The original publication may provide further clarification:

GeoMetrics, Inc., 1979, Aerial gamma ray and magnetic survey, Rock 
Springs, Rawlins, and Cheyenne quadrangles, Wyoming, and the Greeley 
Quadrangle, Colorado: U.S. Dept. Energy, Grand Junction Office 
Rept. GJBX-017(79), 5 vol.