Ernst rifles are discussed in Joe Kindig’s Thoughts on the Kentucky Rifle in Its Golden Age.
He notes that Ernst appears in historical records in Franklin Township in York County, Pennsylvania during the years surrounding the War of 1812, and appears to have died in 1857 suggesting he was active circa 1805 through the 1850s.
Ernst appears to have worked under George Eister as his work has significant similarities. The barrel has the typical brass blade front and notch iron sights commonly seen on American long rifles and is signed "A. Ernst" just behind the rear sight.
This particular rifle is pictured on in the "York School" section of The Kentucky Rifle by Merrill Lindsay.
Most notable is the brass lock plate, Lindsay believes the lock plate may have been made in York by Ernst or one of his apprentices. It may also have been produced by Frederick Sell, given that a Frederick Sell signed rifle also features a brass lock and that Sell appears to have worked under Ernst before starting his own shop. As you can see the full length maple stock has attractive striped figuring at the midsection, brass furniture , and detailed carved designs including rococo motifs on the left side of the butt around the cheekpiece and near the breech with some checkering and silver stud inlays. The ornate patch box also has rococo style designs and it and the side plate have light engraving patterns.