It is a Cooler Master Silent Pro M600 (I bought it in 2009).
Yes, I have a volt meter, but I am no expert at all.
I'd rather buy a new PSU, perhaps an EVGA one.
Regards.
For $15 or $20, you should be able to buy a power-supply tester. I think you need an old but functioning hard disk to connect to it while it's connected to the PSU tester. It's something that the electrically-skittish who might not feel comfortable with a digital multi-meter can do. On the other hand, it's just more crap to buy and put in a toolbox you'd rather not fill.
But 2009 "start-of-service" date should say enough. I have a Seasonic 850W "Gold" 80-plus or whatever in a 5-year-old box I'm selling to a friend as "the whole enchilada, double-caster braked wheels and all." It's been great, and continues to be great. And my friend knows how old it is, and about the PSU. He's getting a great deal, because I'm giving him a good deal.
I wouldn't sell it to someone who might call me six months later with crocodile tears and a panic about "something is wrong with my computer!"
I've had good Seasonics go bad, just outside their 5-year-warranty. They undergo capacitor-aging. Sooner or later, they need to be diagnosed and replaced, or simply replaced if you expect to get anything more out of the board, CPU, RAM and so forth. And letting a computer sleep without hibernating for more than a couple hours at a time* will accelerate the wear and tear on a PSU.
* Like days at a time . . .