After reviewing the images for all 440 patents issued Jan 28, 1908, my best guess is this was the adjuster for a "repair last" (think of shoe tree / shoe stretcher ). The patent in question (877,519) showed a different form of size adjuster, but the only other patent for the date with a turnbuckle was a reissue patent for a walking beam for southern California style cable tool oil well drilling equipment -- much more robust & larger than the piece you show.
A quick way to scan patents by date is using
www.nonesuchtools.com/patent/shotgun.htm . It expedites things to have a .tif viewer capability in your browser; waiting for the U.S. Patent office's .pdf image to generate is a drag.
google patent search (in my opinion) is very flawed & sketchy -- time after time it fails to produce results I know should be shown which is no surprise given the way the product was generated.