Convert from arsheen [Russia] to shackle

Unit Definition (arsheen [Russia])
The Arsheen, also called the Archin, Archine, Archinne, Arschine and Arshin. In the early 18th century, the Tsar Peter the Great issued a ukase redefining the traditional Russian units of length in terms of the English foot. The archin was made equal to 28 English inches, 71.12 centimeters or 16 Vershki.

Unit Definition (shackle)
The shackle is a traditional unit of length used for measuring the lengths of nautical cables and chains, especially anchor chains. Anchor chains are formed by using shackles to join short lengths of chain. When the anchor is dropped and the chain runs out, a seaman counting the number of shackles can report the total length of chain deployed. The size of the unit therefore varied somewhat, depending on the length of the short chains used. In Britain, the unit became standardized in the 16th century at 12.5 fathoms (75 feet or 22.86 meters). In 1949, the Royal Navy adopted a length of 15 fathoms, which is 90 feet or 27.432 meters; this brought the British shackle in line with the U.S. unit, which is usually called the shot.