This part is a kind of semiconductor called AZ12.

Function of this product has Full Wave Rectifying Valve.

Manufacturers : Philips

Image and pinout :

Some of the text within the PDF file :

page 1 2 AZ11 AZ12 sheet 1 FP date 1953.04.04 1999.06.26 [ ... ]

AZ12 PDF Datasheet Download