When first organized some reserve companies included a mix of junior and senior reserves. The War Department would not accept the rolls of such companies. These were reorganized to include either junior or senior reserves, but not both.

What that means is that junior reserve units, such as the 1st and 2nd Alabama, could become PACS regiments (62nd and 63rd Alabama) within a year. By that time it was assumed that all the 17-year olds would have reached their 18th birthday.

Obviously the old men in the 3rd and 4th Alabama reserves could not become anything except older men. At some point in the last days of April 1865 someone decided to call these two units (3rd and 4th Alabama Reserve Regts) the 65th Alabama Regt.

Why, and why not 64th?