The signature on this sextant refers to John Allen (b. 1786), an
"optician and mathematical instrument maker" who appears in Baltimore
city directories from 1810 to 1819, and who was the son of James Allen, a noted
instrument maker in London. John Allen boasted: "As all Instruments sold by
me are graduated by my father’s improved self-correcting engine, for which the
Society of Arts voted him their Gold Medal, on the 19th of May, 1810–they
are warranted and will be kept in repair one year, gratis."
This sextant has a brass frame. The silvered scale is graduated every 20
minutes from -5o to +145o and read by vernier with tangent
screw and magnifier to 1 second of arc. It belonged to the College of the Holy
Cross in Worcester, Massachusetts.
Ref: Deborah J. Warner, "American Octants and Sextants: The Early
Years," Rittenhouse 3 (1989): 86-112, on 89.
John Allen advertisement in the American & Commercial Daily Advertiser
(June 12, 1816).