The item is a exhaust cut-out.  A 'Y" shaped pipe with a rotating valve controlled by a cable (like a choke cable). It permits you to let the exhaust go through the muffler (quieter noise) or direct the exhaust down without going through the muffler (loud noise) & increased horsepower. I used one years ago on a cycle exhaust to surprise people & maybe scare a girl or two.  I found one (vintage now) like I had years ago. There were many newer versions including many electric versions.  So there you are--I am 72 & out of here to ride my cycle & scare some pretty girls.