Look at any supplier data or guide. 127 couples is a standard form for 12V operation with efficient pumping. (Vmax between 14.5V and 15.5V depending on whose data you look at). Don't you think it's a bit weird that 10 of them are in series, on only 28V supply? Sounds to me like the supply is borked too (or is currently set low), and should output 120V max.
Also, if you're just trying to remove heat from the diode modules for high power CW and you're not worried about exact temperature for tuning or cooling below ambient, why not water cool them instead. Lot cheaper and easier.
EDIT:
Melcor also do a 70W 40 mm TEC, CP1.4-127-045L. Qmax 72W, Vmax 15.4V, Imax 8.5A. Compare that with the two I mentioned before. They differ only in thickness. Melcor's three are 3.3, 3.8, and 4.7 mm thick for 72W, 51W, and 33W respectively. So now you should be able to narrow down the options to one. Even if it's not made by Melcor the numbers will be similar.
The simplest way to test empirically for accurate parameters for a 127-couple TEC is to mount it on a water cooled heatsink cooled by cold tap water, then mount a 100W (or 75W) power resistor on top. Turn on tap for moderate flow, no turbulence, then the TEC at 15V input, then slowly send a rising voltage to the resistor, till you balance the hot and cold sides at same temperature. Measure volts and amps to the resistor to get Qmax, and current to TEC to get Imax. The assumed Vmax of 15V is close enough, though it could be 0.5V off either way. If you also want to know the delta T max, turn off the resistor and leave the rest running, then measure temperature of both sides.