AL2O3 means Aluminum Oxide aka Alumina or Sapphire in Electronics
Similar to AL2O3
3D - Three Dimensional 3R3 - 3.3 ohm Resistor 3SR - Three Station Rotating 4P4T - Quad-Pole Quad-Throw 4W - 4-Watt Resistor 4WA - Four Wire Analog 4WAI - 4-Wire Analog Interface