Your Company M might be a transcriptional error with H, or vice versa

You will find a roster in the NPS Soldiers & Sailors System @ http://www.itd.nps.gov/cwss/
However, they seem to be down this evening.

His records may be procured through the service noted in the Red enclosed box above.

.......

Christian Yoke

Enlisted as a Private (date unknown).
"L" Co. MO 6th SM Cavalry
Intra Regimental Company Transfers:
* from company L to company H

Sources used by Historical Data Systems, Inc.:
- Index to Compiled Military Service Records