Its high output voltage was characteristic of crystal elements and its high impedance allowed for direct grid input. The early D-104 mikes used a 1″ thick case and have a large ID tag along with tapped holes for “ring & spring” mounts. The case thickness was reduced in April 1937 and smaller tags were then used and the ring holes eliminated. The “grip” switch stand (“G” Stand) was introduced in January 1938 but didn’t become popular until much later. The early “G” stand bases were gloss black with metal ID tag.