The Mac Junior is one of the rarest of the McElroy bugs for collectors to find. It is also one of the most poorly constructed, being stamped out of sheet metal rather than cast. This model appeared around 1936. The S600 is one of the few bugs ever produced on a teardrop shaped base. Its unique construction makes it another collector's favorite.
Several variations exist.
Interestingly, most S600s are chrome plated, something which McElroy himself thought a poor idea earlier in his career . This is the chrome version of the S600 most people expect to see. It certainly is a snappy looking bug. On the early T-bar bugs, McElroy cast into the bottom of the base that he is the worlds fastest telegrapher. On the S600 and later T-bar bugs, he simply includes that on the front label .