These are big, heavy chunks of mud. Shown with a CD 162 for scale. Both are under-glaze ink stamped "PINCO". On the larger one the "PINCO" is positioned within a rectangle, while on the smaller one only the PINCO name is present. Note that the bigger one has nicely relieved edges at the ends. The larger one is 16 1/4" long and the shorter one is 14 /4" long. Both of them stand 2 1/4" tall measured from the firing rest side to the tangent line of the inverted "U". They are 2 1/2" wide at the widest point. The 1/2" holes at the ends do not go straight through, but are angled slightly. The porcelain near the firing rests is approximately 5/8" thick. Thanks to Colin Jung, Charlie Irons, Rick Soller & Elton Gish for their help in identifying these pieces.

From Elton Gish: They are porcelain tree insulators to cover the conductor cables in areas where tree limbs can rub. There were several size cataloged in the 1950 Joslyn catalog and were made based on patent, 2,361,109:

http://reference.insulators.info/patents/detail/?patent=U2361109