I'm going to guess that it's one of the Evette-Schaeffer type student saxophones that were produced by a hodgepodge of French and Italian manufacturers, and distributed by the Buffet-Crampon company, into the 1980s.  Boosey and Hawkes acquired Buffet-Crampon in 1981, but B-C may have provided Boosey and Hawkes stencil instruments before the acquisition.  There's variation in the details of the 1960s-1980s Evette-Schaeffer type instruments but they were made with the same type of bell key mechanism, with sliding lever linkages between left-pivot keytouches and right-side key cups.  You could compare that example with pictures of Evette-Schaeffers from that era to be sure.