M55, UNKNOWN, PGU
We saw ID requests for this one before and so far I saw no positive response.
Worth to mention that it obviously is a 20x102 (before someone will ammend the thread title).
Here other images from the web.
To what I see this could be sort of a flechette round. Your’s here being a TP.
The unknown projectile is a GPP(General Purpose Projectile) round (i did ask the same question a while ago…)