Survivair (now part of Honeywell) entered the respiratory protection industry too late to be heavily discussed on this website. However, one of their masks is of interest to us, as it bears Davis labels.
This Davis setup dates from the 1980's, and came with a Survivair Panoramic facepiece. It is assumed that near the end of Davis' run, they decided to simply buy facepieces from other companies, instead of manufacturing their own.
Davis designated the facepiece 3020P, following the 3020X and 3040X convention, and used it with the M-1 configuration exclusively.
(This page is mostly here just to contain the photos, I don't have enough info to tell you more than this.)