@Johnny_Reb_1865
Sorry my brevity was confusing, as it usually is.. I got into Fold3 and the CW Data.com, data bases; and here's what I found;
Robert M. Thomas enlisted on 6/20/1861 at Mathews C.H., Virginia in to Capt. A.D. Armistead's Company, light artillery, 61st Regt. Va. Militia. The earliest pay records show him in Co. H, 61St.Va. Militia, Matthews Battalion as a Private.
The 61st Va. Regt {state troops, no longer militia} served from 5/62 until 4/65.
He isn't listed in any Va. 26th, state, militia, Cavalry or volunteers.
The musket you have is in all likelihood a Confederate alteration of a US flint lock musket, and he could have very well used it, but not too likely in an artillery battery. My G-G grandfather was also in an artillery unit, The Petersburg Artillery {thus my handle "lanyard Puller"}, serving as a small part of Jeb Stuarts Horse artillery. He brought home a very nice Colt Navy revolver, a small English telescope, and sawed off shotgun. None of these were issued to him, but more likely came from a poker game or a battlefield pick-up. They are the prized pieces in my collection.