vintage harpoon

This  is not in my field and stating just what I was told,plz do your own investigations, I will help as much as I can,  this is vintage Harpoon log .

The only one I found that looks like it, was made by T.W. Walker ,one of the first made , its instrument to measure speed  and distance travelled by a ship though the water.......I have found no marking on this item and I have no proof its was made by him or later  i told a rope when to a speedo please no I do not have the speedo or rope, just what seen, I am selling.. THIS AS A UNKNOWN ITEM..used condition 

used item..please look at my other items