These are definitely stock factory units as I worked part-time at Design Acoustics in Torrance, California at the time these were in production in the late 1970's. Although the D-1's were also offered in conventional wood cabinets, far more of the metal cabinet versions were produced. The dispersion cones suspended in front of the tweeter were cast in house from a resin material. The reason they were used was because original owner and designer George Sioles wanted wide dispersion from all of his models. He chose the Peerless cone tweeter over a dome because they cost far less! (lol)
George sold Design Acoustics to Audio-Technica in 1980 and the operation was moved to Stowe, Ohio although none of the pre-existing models were continued. Audio-Technica designed the "PS" Point Source models in house and they had nothing in common with the George Sioles ownership "D" series models, well apart from putting the woofers in odd places...(lol)