This part is a kind of semiconductor called TAA550.

Function of this product has Linear Integrated Circuit.

Manufacturers : ETC

Image and pinout :

Some of the text within the PDF file :

The TTA550 is supplied in 3 groups of stabilized voltage identified by a letter after the code, as shown in the "Ordering Numbers"
Features
1. Low Temperature Coefficient
2. Low Zener Resistance [ ... ]

TAA550 PDF Datasheet Download