I think I answered my own question, but I'd like to know that my research is valid. The chips say M12L16161, so 16 x 8 = 128kbit / 8 = 16mb?

Yes, that is a TNT2 m64 with 16MB of RAM. It is not a Vanta chip (they were labelled with the Vanta name horizontally on the chip) but it might have been sold as one. The Vanta was just a poorly binned TNT2 m64 so it was clocked slower.

What is it good for? Nothing much really. I sometimes use one for testing newly acquired motherboards.

Good for period-correct mid-range system from 1999. If you had money to burn you would have bought a TNT2-Ultra or maybe a G400Max or Voodoo3-3000. If - like me at the time - you were a poor student, you'd probably buy one of these, as they offered a big upgrade from previous bargain-basement stuff (I previously had an ATi Rage Pro II) at about half the price of an Ultra.

Of course, the 'realistic 1999 experience' was slow, due to this TNT2-M64, only 64MB of RAM, some old 5400rpm HDD (or worse) and at best a Celeron CPU, so unless you're nostalgic for that too, you might want to go for the Ultra with a P3 and other nice stuff after all 😉