Zonie, I'm not familiar with your source, Merwyn Carey, but he seems to be at odds with other sources.
Henry Kauffman in
The Pennsylvania-Kentucky Rifle in his section on Henry Leman page 289 writes, "Conestoga rifles which name Leman is thought to have used for rifles of poorer quality than his standard products."
Frank M. Sellers in
American Gunsmiths, page 65, has this entry "CONESTOGA RIFLE WORKS, Lancaster, Pennsylvania. Trade name used by Henry Leman."
Also Charles E. Hanson, Jr. in his seminal article "Henry E. Leman -- Riflemaker" published in
The Museum Of The Fur Trade Quarterly, Volume 20, No. 4, Winter 1984 has, "There are cheaper quality Leman guns which bear only the stamp, 'Conestoga Rifle Works,' but I am unable to determine when this practice began."
A friend of mine has an antique rifle marked "CONESTOGA RIFLE WORKS" that looks just like a typical Leman rifle. It is percussion.
Obviously, these percussion arms marked "CONESTOGA RIFLE WORKS" do not date to 1780.
Cajun72's lock is most likely a product on Henry Leman's factory.