Aug 1976 Canon City Colo Disk shap duration 2 min just came over mountain and flew by

this has been some time ago but told a friend about it and he said to submit a report.  When on duty at the Colorado State Prison as a corrcetional officer preforming tower duty on the primiter of the prison, at approx date and time stated above,a silver looking oval disk shaped objict came over the mountain ridge about 200 yrds away.  It was spinning about 25-35 rev counter clockwise and moving along the ridge about 20mph.  It looked to be aprox 100 feet in length,it was making a low pitch humming sound. 
This took a while to process as it was strange to see, i think i put this on my shift report.  Then when got off shift went to the Canon City P.d.  told them about it.  
The sighting did leave me somewhat disoriented and poor sleeping for about 2 weeks.
Witness indicates that the date of the sighting is approximate.  PD