The muster-in roll, dated "30 Sept" 1862, also included (in alphabetical order by surname) those mustered in October. On this list, Otis is shown as age 20. The descriptive roll, which shows no date, would list Otis as age 23. The Maine Adjutant Reports would repeat this age, as does the muster-out rolls.
Otis C Holt was listed as a carpenter, single, b. Peru, Maine, res: Canton, ME
Looking into the 1850 census for Peru (and the surrounding communities), only one Otis Holt was found, with Erastus and Lucinda Holt in Peru. The 1860 census shows two of this name in Peru, both of them age 17, one with Erastus, and the other a farm laborer in the William Irish household. I suspected those were the same person, enumerated at different times.
Actually, both Holt brothers had enlisted with the 5th Maine: Artemas C with Co E on 2 May 1861 (res: Peru, b.Weld, ME; 5' 4", blue eyes, dark hair, Lt complexion), and Otis C with Co K on 28 May '61 (res+ b.Peru, ME; 6', blue eyes, Lt hair and comp.). Both were listed as age 19. Though seen on the muster-in roll, Artemas was not mustered in, as noted in a later adjutant report. Otis was must-in on 24 June, and received a disability discharge on 22 May 1862.
In the summer of 1862, both Artemas Cooper Holt and Otis Charles Holt enlisted for the quota of Canton, Maine when a company of nine-month troops were being raised. Neither of them used their given names, however, they reversed them. Below are their signatures on the enlistment sheet for the town, which was dated 25 August 1862.
Cooper A Holt was mustered out of the 23rd Maine on 15 July 1863, while Otis C was mustered out of the 27th Maine on 17 July 1863. When September came around, along with it came another enlistment drive, for 3-year troops. One Charles O Holt of Peru, born same, a mechanic, age 20, 6', blue eyes, brown hair, light complexion, enlisted on 10 Sept 1863, and must-in as a sergeant in Co G. He would serve until 20 Aug 1865. The following year, he would apply for a pension (see index card on right).
"Charles O" Holt, alias "Otis C", alias "Cooper A" Holt.
He died 26 Jan 1920 in Lewiston, ME, aged 77 y,9 das (or b.17 Jan 1843)
Thanks to the availability of most of the company enlistment sheets, where the volunteers would sign their names (unless unable to, when an X and "his mark" would instead be written), a comparison of the names can be made. Though I am no expert, it certainly looks like the "Otis C" and "Cooper A" in the left column have similarities, particularly in the 'H' of Holt. The same seems true of "Charles O" and "Otis C" on the right. Unfortunately, the letter 'C' on both sides do look alike! The "A G Holt" signature is almost surely not written by the same person whose signatures are below it.
Perhaps by ordering the pension file for Otis Charles (aka Charles Otis), it may give me more information about why these aliases were used.