Nantucket Signals dates the flag to 1851; the additional painted source is labelled 1840–1850.
James Loper’s Nantucket whaling career is dated 1837–1860, or from 1838 in Nantucket Signals. Known owners include Levi Starbuck, George F. Folger and Henry Coffin. Levi Starbuck was agent through 1846, followed by Obed Starbuck in 1851–1855. She was sold to New York in 1860.
Keep the explicit scope label independent; no alias or company identity is inferred.