Unidentified Hardware at 20 Vine Street

The variety of styles, mechanisms and alterations found in old windows continues to surprise me.  Usually I can identify what they are, but this one has me stumped.

These are inset in the jambs and used to hold the upper and lower sash in place.  Bwhat is it called. when did they make them, and how did they work?  The house it came from was built in 1907.