Hello
I have been assigned to Fox units for over 7 years.
Your example was from a Chemical Company
The Recon platoon was the sixth platoon in this unit, hence the six in 615
Normally the first five were HQ,plt and then Decon Plts, 5th is Smoke and 6th in Fox Recon.
615 also means that it was in the first squad (2per squad) hence the one in 615. Secon squad for example would be 625, etc
The letter in front on 615 are RCN for Recon
Smoke tracks wouls have, SMK 515, etc
Hope this helps.
Those Fox vehicle were on loan from German in 1991.
Ryszard