Type D (1905 to 1913), D-3 and D-4 (1913) Previous
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The early Type D mercury-motor meter used a new material (Bakelite) for the mercury chambers and the armature disk had a small copper float soldered to it to keep the disk off the bottom of the chamber. Also, the mercury chamber was designed with a pocket that would capture the mercury in the chamber if the meter ever got inverted, to prevent the mercury leaking out of the chamber. There was only one major flaw with this version and that was the mercury ate through the solder holding the float in place, making the armature sink and stopping the meter.

In 1907, a new version of the D came out, and had some minor changes in the design, including a cork float which replaced the older copper floats.

The D-3 and D-4 were produced only briefly, and no data exists on these other than they were transitional models between the later D and D-5 meters.

No picture available of these models.