This is what PMI is calling a "Matched Pair" of Studio Projects microphones.
-33~-34dB +/-.5dB, is marked by a red dot on the packaging
-35~-36dB +/-.5dB, is marked by a green dot on the packaging
-36~-37dB +/-.5dB, is marked by a black dot on the packaging
Whereas the Sound Room for example...
"Matched pairs are selected from the test areas of different manufacturing labs and tested in the anechoic chamber (and ancillary facilities) at a famous Moscow-based Microphone Lab. As with all of our microphones, they are chosen for assembly and finish and then tested to meet specific acoustic and electronic modeling. Mics in matched assemblies are tested individually and then as pairs. Once matching is complete, they are boxed - along with proof of frequency response analysis. From there, the mics are sent to our "sister" studio in Moscow, where they are tested and checked again in various acoustic source tests and further documentation is attached.
The mics that pass all these tests are shipped to the SOUND ROOM, where they are checked again in our studios and readied for shipment. This may include changing packing/shipping materiel, fitting to cedar boxes (from the Ozark Mountains), final cosmetic checks and repackaging of the assorted documentation and new (US made) accessories."
I think the Studio Projects microphones have such poor quality control PMI had to put colored dots on their microphone boxes because the microphones are just cheap Chinese made mics so they couldn't fix the quality control problems so they just added colored dots instead, and called them matched.