Here's the SCR used across the board to build devices for training commands.
Here's the official write up:
Glassivated PNPN devices designed for high volume consumer applications such as temperature, light, and speed control; process and remote control, and warning systems where reliability of operation is important.
Glassivated Surface for Reliability and Uniformity
Power Rated at Economical Prices
Practical Level Triggering and Holding Characteristics
Flat, Rugged, Thermopad Construction for Low Thermal Resistance, High Heat,