Hi. Greetings to everyone in this forum. I'm a collector of military items from Spain. I'm looking information about the markings that appear on the safety catches, for the .303 "Vickers Medium Machine Gun. As shown in the photo, a double arrow and the letter "A" appear. I would like to know what these marks indicate and if you know the period of the safety catches. Can you help me? Thank you so much to everybody. http://i65.tinypic.com/d78tw.jpg