agb,
We seem to be in disagreement on the semantics of whether this cartridge was "designed for" or "used in" the RPG trainer. Clearly it was used in the trainer, but I maintain that it was not "designed" for it, nor is it a spotter. I have sectioned a specimen of this cartridge and can conform that it contains no spotting charge, simply a tracer capsule. This projectile, with identical color code, also exists in Czech 7.62x45mm from the 1950's which further reinforces the origins and intent of this cartridge type to be a short range trainer for rifles and machine guns.
Again, I refer you to the recent discussion on this round at the IAA cartridge discussion forum, where this round is clearly identified as a short range tracer for use in all 7.62x39mm chambered weapons.