This is one of the later versions of 400A power transistor module made by Fuji Electric of Japan. As a part owner of Fanuc Ltd, Fuji have built millions of components on behalve of Fanuc for various electronic devices.
In this instance the A50L-0001-0344 is also known as 2MBI400TC-060 in a special FANUC only package design. These transistors were fitted in ALPHA series Fanuc spindle, power module and servo amplifier modules and units.
This IGBT transistor is a two gate 400Amp per gate at 600 volt. These are always in stock and are genuine Fuji power transistor modules.