I found this. Which ...
1. Re-confirms there was a 3rd Battalion with the Louisiana State National Guard.
2. Gives a brief history regarding how and when the L.S.N.G. was established.
3. Invitation has "L.S.N.G." printed on it.
~ * ~
~ 1893 Invitation ~
"THE MILITARY BALL OF THE THIRD BATTALION INFANTRY SO. LOUISIANA NATIONAL GUARD, (Which Includes ) "LOUISIANA RIFLES, CONTINENTAL GUARDS JR. AND THE CRESENT CITY GRAYS."
AT THE "WASHINGTON ARTILLERY HALL, Thursday Evening, February 2nd 1893.
THE INVITATION IS SIGNED BY MR. J. B. STROTHER, Compliments of GENNIE ASHBY.
"Strickly Military or Costume de Riguer."
THE INVITATION IS 5" X 3 3/4" IN SIZE.
~ HISTORY ~
The 2nd Battalion, 156th Infantry Regiment was originally organized 9 and 17 May 1861 as the 2d and 3d Louisiana Volunteer Infantry Regiments and mustered into Confederate service at New Orleans. The 2d Louisiana Volunteer Infantry Regiment surrendered on 9 April 1865 at Appomattox, VA, with the Army of Northern Virginia; the 3d Louisiana Volunteer Infantry Regiment disbanded on 20 May 1865 at Shreveport, LA.
The 2d and 3d Louisiana Volunteer Infantry Regiments reconstituted on 30 March 1878 as the Special Militia Force to include separate companies and battalions outside Orleans Parish; its elements organized between 1878-1890 embracing fifteen companies by 1890. They were reorganized in part on 26 December 1891 as the 1st and 2d Battalions of Infantry and transferred to the Louisiana State National Guard . The battalions consolidated on 17 March 1896 to form the 1st Regiment of Infantry with Headquarters at Baton Rouge.
The unit was mustered into Federal service between 8-18 May 1898 at New Orleans as the 1st Louisiana Volunteer Infantry and mustered out of Federal service on 3 October 1898 at Jacksonville, FL. It was reorganized on 8 August 1899 in the Louisiana State National Guard as the 1st Battalion of Infantry with Headquarters at Monroe. It was expanded, reorganized, and redesignated on 6 December 1904 as the 1st Regiment of Infantry with Headquarters at Monroe. The Louisiana State National Guard was meanwhile redesignated in 1910 as the Louisiana National Guard.