As a 'Nelson' rifle, there's nothing - but as a 'Dickson, Nelson' - there's this:
From 'Flayderman's Guide'...
"Dickson, Nelson Carbine and Rifle made by Dickson, Nelson & Co.
Total quantity estimated 3600 at Adairsville, Georgia, (1862-3), Macon (1863-4) and Dawson, Georgia, February 1864, to April 1865.
The firm was founded by William Dickson and Owen O. Nelson, and was known as the 'Shakanoosa Arms Company'.
Approximately .58 caliber, muzzleloaders. Lockplates styled after U.S. Model 1841 pattern.
Finish unknown. Markings generally of brass. Stock of Walnut or Cherry.
Lockplate marking: Dickson/Nelson & Co. C.S. - forward of hammer. At rear of lock, marked vertically: ALA./(date). Barrel may also be marked: ALA (date), at breech. Stocks may bear stamping F. Zundt.
Surviving specimens are rare. Most bear lock date '1865'.
Very seldom seen date '1864' and only one recorded '1863' on an unattached lockplate thus far."
That said - these are pricy - starting at $9,500 in 'fair' condition and around $27,500 in 'very good' condition, and anyone familiar with the NRA's 'antique arms' grading standards for those conditions isn't going to have anything eye-popping to look at.
The above post regarding their probable use as a repair/rebuild shop is likely on the money.
Many of the weapons in storage in the various State Arsenals were of earlier manufacture, and getting them re-conditioned and ready for a combat role occupied a large number of small firms.
Vaya,
Scouts Out!