So why Big Twin Island? What sense does Big and Little Twins make?? Why not Big and Little Sisiters, or Pike and Minnow Islands? I don't know, but that's what I grew up calling them. The island is somewhat overgrown and has some short (<10') cliffs. In spring there are often ospreys and/or loons nesting on Little Twin so please don't disturb them (generally they seem used to people stopping on Big Twin since it is a popular swimming spot).
The cache is a camoflaged locking plastic sandwich container, yes with a few little treasures, only moderately well hidden.