Jim All the Bosch magnetos I have seen have a serial number on the main frame. From this number it can be determined what year the mag was manufactured. The numbers are quite small compared to the Bosch model numbers/letters. If the serial numbers fit into the 1,567,966 to 1,758,030 range than it was made in 1914. If not in this sequence and you wish to know the year send the number on your mag,I can then identify what the year of manufacture is.