I only found this. From here you will need to obtain his service record file to get the complete time line of his service. See the note above for how to obtain these.

George Martin

David Teubner

Enlisted as a Corporal
"D" Co. MO 7th SM Cavalry

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From the NPS Soldiers and Sailors System

David Teubner (First_Last)
Regiment Name 7 Missouri S.M. Cav.
Side Union
Company F&S
Soldier's Rank_In 6 Corp.
Soldier's Rank_Out Pvt.

Interesting that he served on the Field and Staff in this listing!