US 1861s were very highly regarded and sought after. As a result, they were sometimes issued almost as a form of patronage (of sorts) to certain units not necessarily based on the needs of front line troops, but almost it seems as a reward or a recruiting tool. There is that famous example that is found in "History of the First-Tenth-Twenty-ninth Maine Regiment," by Maj. John M. Gould; (1871), page 89.
"Oct. 21st [1861], new muskets were delivered to the men, and this furnished another excuse for a hearty growl from the 1st Mainers. "Had we not been promised a new blue uniform and Springfield muskets?" To be sure we had the blue uniform and a good outfit in every way, "but look at these Enfield muskets," said they, "with their blued barrels and wood that no man can name!" They were not a bad weapon, however, differing little from the Springfield, in actual efficiency, weight, length, and caliber, but far behind in point of workmanship. For a while we kept them blued, then orders were issued to rub them bright and we kept them so ever after."
It is worth noting that the 90 day 1st Maine troops reenlisted partially on the promise of receiving new US model 1861s if they did so, having just turned in their US 1855s. Whatever the case, clearly these two US 1861s did not see the same hard use as many other surviving examples. Or perhaps they were just very well maintained. Whatever the case, these are both very nice specimens. You are fortunate to have them in your collection.