The earliest of this form of brace dates to the 1700's. These early ones are often referred to as "gent's braces." What made them "gent's" braces is the screw detent for the bits -- pros used one or another of quick release mechanisms.
By the mid-1800s they were just easier to make cheaply, and were more common. The original screw would have been a thumb screw, so yes, yours has been replaced.