Quote:
It's an inert training projectile (blue) re-mounted on expended brass (empty). Most anyone who passed through the A-10 community got one as a farewell gift of some sort, usually engraved.
Correct. It's a empty/spent casing holding a PGU-15/B TP (Target Practice) projectile.
There's also:
PGU-14/B API (Armor Piercing Incendiary) (DU - depleted uranium)
PGU-13/B HEI (High Explosive Incendiary)