Originally Posted by
sweetspot
It is DT Swiss m1900 spline 650b. Not the newest version because this wheel is at least 3 years old.
Should email DT to be sure; as you're wanting to take an MTB wheelset and retrofit to roadie-thru-axle sized endcaps.
Looking back as far as the MY2017 PDF charts they have posted, 12mm endcaps aren't even listed as an option for M1900 Spline wheels.