I have six of the volumes on Masters of Jazz.
Volume 1 (1937-39)--I don't think any of this volume is rare.
Volume 3 (1943): There's just one track of Lester with Basie, an AFRS G.I. Jive Transcription.
Volume 4 (1944): No live material.
Volume 5 (1944): No live material.
Volume 6 (1944): This volume has some broadcasts, Basie from the Lincoln Hotel (one track), the Jammin' the Blues soundtrack, broadcast with Hot Lips Page and Charlie Barnett (1940)j, and Lee and Lester Young broadcast (1942).
Volume 7 (1945-46): Only live material is a JATP recording.