2N3772
TO-3 case, Regulator transistors, 2 or more used in Ashtron Power Supplies.

2N3772   HIGH POWER NPN SILICON TRANSISTOR

TO-3 case, Regulator transistor, Ashtron power supplies use 2 or 4. 
In larger 13.8 volt DC high current Power Supplies may use 6 or more.

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DESCRIPTION:
The 2N3772 is a silicon epitaxial-base NPN transistor mounted in a Jedec TO-3 metal case.
The 2N3772, replaces: 2N3771, 2N3772, & 2N3773. 
They are intended for power supply regulator and switching applications.