so ABU carried the SLAR and ABV didn’t?
From French medias, the two (ABU/OV-1B and ABV/OV-1C) in flight (the complete special french registration seems to be F-MABU and F-MABV) :

from text, it seems that other aircrafts, coded ABA, ABB and ABC, were test flown in France with a mix of french roundels and US ones….no pictures found till now.