The top bit seems to mean 30-550-DEFA-210. So 30 mm, 550 series cannon, the דפר meaning DEFA (aka dft or defer), and then the projectile code. The 210 is a bit weird as the first generation TP rounds with tombac driving bands were 2101 (M1 design projectile) and 2102 (M2 projectile) according to the book I have? Checking the same book, the rear of this projectile doesn't match either the 2101 and 2012. The cavity suggests the presence of a tracer (now removed), which wasn't present in either the 2101 or 2102.