I have many porcelain lag screw insulators similar to this, but this is the only one I have found in this exact style. P.P. 1929 is recess-embossed on one side, and PAT. 4-16-29 is recess-embossed on the other. I know that that patent was for lag screw insulators and was patented by William D. Kyle on April 16, 1929. Also I believe that this insulator was made by Porcelain Products Inc. (PLEASE correct me if I'm wrong). I was wondering if anyone knows how old this piece is. Any information about this piece would be appreciated!