(British)

1a. Glasses, spectacles. A cockney shortening of binoculars, sometimes spelled binns. The term has been in use at least since the 1930s and is still heard.

1b. The eyes. An extension of the previous usage.

2a. Headphones. Part of the jargon of recording engineers and rock musicians in the late 1960s; the term was eagerly picked up by hi-fi enthusiasts and musos in the 1970s, although cans is more prevalent in this context.

2b. Hi-fi or concert speakers. By extension from the above sense.