This sextant was owned by Frederick L. Waterhouse. Frederick was born in Searsport in 1841; his four brothers all became ship captains, but he only became a mate. After his service in the Civil War, he settled in Montville, Maine, never becoming a sea captain. His initials are inlaid into the cover of the sextant box, something he could well have done, a not uncommon practice amongst ship officers.
The sextant itself is a fine English Spencer, Browning & Rust instrument; it would have been more expensive than the more common wooden framed octants. When he got it, he was probably intending a career at sea.