Along with petro. items I also collect and restore Delco-Light electric plants. I have 12 plants, 6 of which run and do generate 32 volts of direct current electicity for farm use. between 1916 when they were invented until 1947. When the REA found their way to rural ,America. The porcelain signs are very hard to find, as there were not a lot of them made. the cheapest one I have ever found was at Peotone Ill. about two years ago, $1600.00. I passed on it. I settled for a couple of SST ones from John Mancino which were in great shape. The word DELCO is actually an acronym meaning Dayton Engineering Laboratory Company, which Gen. Motors still uses today.