This small lens piece was turned in at the Meadowlands Environment Center quite some time ago and was only recently brought to our attention. Please e-mail us via the "e-mail me" button in the left-hand column of this blog if you want to claim it. Post a comment if you think you know what it is. Thanks.
The Meadowlands Nature Blog
I think it is eyepiece with adjustable diopter, from either a really old camera,or more likely from an older pair of binoculars.
This ocular belonged to Mr. Harold Benchman a renown 17th. century bird watcher who obsessively watched birds in the Meadowlands. His scorned wife Lucy Larrain killed Mr. Benchman while he was bird watching and after he claimed that birds were more important than her. The missing ocular was never recovered until today