Hi to you all from a member the UK. I have owned many cars throughout the last fifty years including some interesting cars from the USA. I have recently purchased a 1932 BSA Family Four (four seats, three wheels, two cylinders). In one of the many boxes containing parts for this car was an interesting spark plug. I will attempt to attach a picture but if that fails here is a description. 18mm thread size with three brass cooling fins at the top and a high quality knurled screew to hold the HT lead. The ceramic parallel insulation is black with yellow script marked "HERZ" on one side and "BOUGIE MERCEDES" on the other. Any ideas of date or any other info?