This is a scoring session for the movie G.I. Blues, but it is unknown exactly when the session took place.
The tracks listed as being on the Elvis One releases From Santa Monica Boulevard, Los Angeles, California - Part 3 (The Bootleg Series Vol. 36) and Elvis Presley In G.I. Blues - Part 1 (The Bootleg Series Vol. 48) appear to be lifted from the Blu-Ray release of G.I. Blues, where the "Score" can be found on a separate track of the Blu-Ray disc, some of it without talking etc, which can be heard in the soundtrack of the movie.
All timings in the 'Musical Breakdown' below are taken from the Blu-Ray release of the movie.
Thanks to David English for research.