The CD 1006 has been documented as being placed in service on the Philadelphia-to-Baltimore section of the Magnetic Telegraph Company line. They were used to replace the original crude form of insulation on that line. An exact date of this rebuilding is not known, but most likely it took place between October 6, 1846, and April 6, 1847, when James Reid was manager of the company. The V-shaped projection on either side most likely served as a means to help hold the block in place, preventing it from horizontal slippage from the strain caused by the weight of the wire.
CD 1006 (above), a "baby block", shown in three profiles of a sharp v-shaped projection ...
and two profiles of a more rounded v-shaped projection.
The CD 1007 is very similar to the insulator described above, but differs in that it has rounded projections at its center. At least one whole example surfaced in Ohio, and pieces of them have been located along the route of an early telegraph line constructed in Ohio.
CD 1007 (above), a "baby block", shown in three profiles with a rounded projection.