This is an unfinished whalebone Gauging Rod about 52" in length, made from the heavy bone of a sperm whale's lower jaw (the area below the teeth).  It is 3/4" square at the upper end and tapers down to a knife edge at its lower end, which is covered with a v-shaped fitting of non-ferrous metal (probably brass), 1-5/8" long .  One side  has 2 deep incised parallel lines running the length of the rod. The numbers of gallons for calculations were never engraved. If present, they would have been used to determine the size of the cask.  Nice condition with slight warp, not unexpected, considering its length.

Attributed to Sag Harbor Whaling Master Barney Green, ca. 1850's.  From a collection of various scrimshaw items descended in the Green family.   

In the whaling period, whale oil casks were measured in "barrels".  A barrel was 31-1/2 gallons.  The cask's capacity in barrels, would be determined by laying it on its side and inserting the rod diagonally into the bung hole to the far corner.  The number of gallons, normally engraved on the rod would be read at the bung opening and would be divided by 31-1/2, thus determining the capacity of the cask.  

SORRY, SOLD