Terry and George,
Meaning no disrespect, the 5th Cavalry Regiment MSM that William Penick commanded was disbanded in February 1863 because of its many deprecations. Subsequent to this, the 13th Cav MSM was redesignated the 5th Cav MSM but was always referred to officially as 5th Cav MSM (new) to differentiate it from "Penick's Thieves." The reputation of Colonel Penick's regiment was so bad that when it was disbanded its personnel were discharged and not carried into other units of the MSM. Unfortunately for southern sympathizers of northwest MO, a number of these bitter radical northerners spent the rest of the war making life miserable for southerners of that region. The records of the older 5th regiment referred to it henceforth as 5th Cav MSM (old) so that officialdom and everybody else would not confuse these VERY different units. This can be very confounding. I have had to write about this a lot, so I am cautious not to fall into this well-disguised trap. Terry, this is a natural mistake.
Eppstein's Battalion MSM was organized at Boonville, Cooper County, in March 1862 of mostly German-Americans. Eppstein's battalion was in some lively scrapes in Saline County fighting Confederate behind-Union-lines recruiting units and in Jackson County fighting Quantrill's band all between March and July. In July 1862, since it was not a full regiment, it was placed into the newly organized 13th Cav MSM with other similar "orphan" Cav MSM units.
Then, just to confuse everybody, in February 1863, as I wrote above, the 13th Cav MSM was re-designated as the 5th Cav MSM (new). Clear as mud, right?
George, there are many places to look for records of the exploits of Eppstein's Battalion, the 13th Cav MSM, and the 5th Cav MSM (new)[as well as the old] in the guerrilla warfare of Missouri. Somebody has attempted to record all that while listing as endnotes most of the available sources for further reading. Yes, somebody did that to help in a case just such as this. You may view these books (one about 1862, one about 1863, 1864 is in work) using interlibrary loan or they are still in print--whichever method you prefer. Now, what did I do with that author's name???