It is always a shame that usually at least one GEC brick would be casually replaced by a MA60, thus defeating the purpose of full cut-off lighting around airports!The later Philips family of low pressure sodium lanterns (the MA50, MA60 and MA90) can also be configured to give a cut-off optical distribution. It requires the installer to move the bulbholder further into the canopy of the lantern - positions are clearly marked. However, this requires the installer to have the knowledge to do so...I'm glad that Philips do not market their MA series/SRS201s as full cut-off lanterns as, thanks to their shallow U-shaped bowls, such a claim would be a blatant lie!
Of the two types of lantern (the GEC brick and the Philips SRS series) the GEC brick can claim to be the only truly full cut-off SOX lantern, but only when it's fitted with the flat-glass panel. The GEC bricks with the bowls that protrude below the canopy will still leak some light above the horizon.