alternator or voltage reg?

[Glen]

Car is a 1990 190E 2.6, 5-speed.
177K miles, unknown if alt is original or not, however, I changed the voltage regulator 6 months ago when it failed causing a dead battery.

Today's symptoms:
battery and ABS idiot lights came on

Voltage at battery with engine on: 13.9V

If I disconnect the negative terminal,
voltage reads ~10V at idle, increases as RPM goes up with peaks to ~16V.

So, does a defective voltage regulator (remember it's only 6 mo. old) make the most sense or is the alternator also suspect?

Thanks!