Hiatt "Come alongs" or Nippers

Hi I have a set of Nickle plated Hiatt come alongs they are very plain with plane center pivot covers, they are marked on one side only and are marked "HIATT" that is the only detail on them....Can you provide any information on them? Age? Use? CID? Value? Rarety? These seem to be precision engineered (almost) and are of exceptional strength. I intend to keep these in my collection but unfortunatly know nothing about nippers or how this style would have been used. Please post..... Thanks

Jack Tanis has a lot of information online about these items at http://www.editing.org.uk/tanis/restraints2.htm.