Hello, Anna:

You were asking how old the flintlocks/firelocks might be. While this is speaking of TN flintlocks, it just might give you an idea of the antiquity: I posted this on the TN Board, and Mr. Greg Biggs posted his answer below.
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{For the Louisville Courier}
Ancient Firelocks

Editors of the Courier: In your issue of today you tell us that amongst the old arms brought from Fort Donaldson for repair is one bearing the date of 1761. This is certainly an ancient "firelock," but if your curiosity runs in the line of old guns, by stepping into the State Armory on College Hill, you may see one still older by twenty years, and many others made during the "reign of the Georges." Or should your curiosity impel you to see to what great perfection the art of gun making has been carried, it can be gratified with the inspection of the ne plus ultra of war weapons, the "Morse Carbine," besides many other interesting objects that will repay you for the visit.
Nashville Oct. 28, '61 SENEX

(Daily Nashville Patriot [Nashville, TN] 03 Nov 1861) Page 2

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Hoyt:

The Tennessee State Armory was loaded with flintlocks at the start of the war. Many of them went to the Tennessee regiments that fought at Mill Springs in January1862 in the cold drizzle of that day - and they had a hard time getting them to fire. Meanwhile, the 15th Mississippi has Jeff David rifles with percussion caps and just blazed away!

Some of these obviously made their way to Fort Donelson as well as the article noted. According to a source that I found some years ago many of the flintlocks in the state armory were last used at New Orleans in 1815 by the Tennessee troops there.

Greg Biggs