[Hallicrafters] SR-540?

[Jim Liles]

Noticed an SR-540 on the auction site.  Note that the original SR-540 did not have the notch or CW filter like the SR-400.  The under chassis shot clearly indicates that it has at least the notch filter and we cannot see enough of the rest to determine if it has the CW filter.  Has anyone any information that would indicate that the SR-540 ever included the notch or CW filter?  Were they possibly up grades after the SR-400 came to market.  Seems the genealogy of some of these great and enigmatic radio's is relegated to history.  Kindest regards Jim K9AXN