• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

ID Transformer Help / testing

I have a transformer that I do not know where it came from. The only factory marking on it is 139195. In masking tape is written 350 - 0 - 350, 12.6 VAC, 5(something) heat + 5V LI (something). I would get a photo but the camera on my phone is not working. Its fairly beefy transformer, kinda looks like a dynaco transformer just on steroids.

Is this transformer worth building a tube amp around?
How do I test said transformer?
What are my amp build options?