.50" BAT again (sorry)


Hi to all,
I’ve come to a hold up trying to catalouge my collection again,this time with .50" BAT spotting rounds.
The round on the left I know to be a X7E1 with the detonator in the nose of the projectile from the mid 60’s and from info gleamed from TonyE’s posts on here and other forums that the round on the right is a XL7E1 without the detonator in the projectile,this example is 1977 dated.
I’m trying to find out if the others, all spotting/tracer rounds,probabley a progression from the X7E1 to the XL7E1, had different X or XL numbers?