Bowl-back (or round-back) mandolin, likely built around the late 1800s to early 1900s by American makers like Lyon & Healy (such as their Washburn or Carl Fischer lines) or similar Neapolitan-style instrument
A bowl-back mandolin (often called a "potato bug" or "beetle back" in the United States) built between the late 1800s and early 1900s represents the height of the instrument's late-19th-century "Golden Age".