Crossbone Gundam Supplier.

[Mafty]

So it's established that the three Crossbone Gundams as well as the limited mass production Flint units, are from SNRI, but were "given" to Crossbone Vanguard. How did this happen? Did Crossbone Vanguard have a cohort in SNRI who stole the units? Or did they simply buy them under the table (Sheridan Ronah who leads her own Crossbone Branch seemed to have money)?

[Seto Kaiba]

So it's established that the three Crossbone Gundams as well as the limited mass production Flint units, are from SNRI, but were "given" to Crossbone Vanguard. How did this happen? Did Crossbone Vanguard have a cohort in SNRI who stole the units? Or did they simply buy them under the table (Sheridan Ronah who leads her own Crossbone Branch seemed to have money)?

No, they weren't stolen or purchased "under the table".

SNRI loaned three F97 Gundam technology demonstrators to the Crossbone Vanguard in order to clandestinely collect data on their performance in actual combat conditions. That data was being used to refine the production version of the F97 (the Flint) that SNRI was developing for sale to the Earth Federation Forces. Once the Juptier Empire began advancing into the inner solar system, SNRI discontinued the F97E out of fear that their connection to the Crossbone Vanguard would be exposed and they attempted to salvage the program by modifying the design further into the F99 Record Breaker.