Before revision: Marine sandglass, helmsman's , in a four-column wood stand A marine sandglass is a timepiece of simple design that is a relative of the common hourglass, a marine (nautical) instrument known since the 14th century (although reasonably presumed to be of very ancient use and origin).
After revision: Marine sandglass, c.a.1750Helmsman's , in a four-column wood stand A marine sandglass is a timepiece of simple design that is a relative of the common hourglass, a marine (nautical) instrument known since the 14th century (although reasonably presumed to be of very ancient use and origin).