$binary

Pass "true" to save the BLOB as a document (must also pass $expand={blobAttributeName})

Description

$binary allows you to save the BLOB as a document. You must also use the $expand command in conjunction with it.

When you make the following request:

GET  /rest/Company(11)/blobAtt?$binary=true&$expand=blobAtt

You will be asked where to save the BLOB to disk: