This is one of the semiconductor types. This part name is TAA550.
This product has Monolithic integrated voltage stabilizer functions.
Manufacturers of product is ETC. The package is TO-18 type.
See the preview image and the PDF file for more information.
Image and pinout :
TAA550 PDF Datasheet
Some of the text files within the PDF file
The TAA550 is a monolithic integrated voltage stabilizer in a TO-18 two pins metal case. It is especially designed as voltage supplier for varicap diodes in television tuners.
1. Low temperature coefficient
2. Low zener resistance
[ … ]
Please refer to the file for details.