The following pdf file contains all of the resized Project Blue Book documents below and is now housed on the NICAP site for security reasons.
The original over-sized docs from the Blue Book site are cited below:
Frames 983 - 1002
April 3, 1949. 1 mile SE of Dillon, Montana (BBU)
Time: 11:50 hours
Observers: Gosto Miller, operator of construction company, commercial pilot
and aviation engineer
Number of objects: One
Size: 15 to 25 feet in diameter
Color: Bright upper side, lower side blue grey
Altitude: 3000 to 5000 feet
Speed: 1000 MPH, so fast object seemed to blur
Maneuvers: Descending to 700' to 1000', appeared to be rocking or rotating in
a semi circle. The object rapidly disappeared over the mountains.
Apparent construction: Metal, like aluminum
Comments: By Capt. John P. Brynildsen, District Commander, "Particular attention is drawn to the fact that the direction of travel of the unconventional aircraft conforms with the radio beams in the Dillon range"