I am “trying” to restore a prewar AF ‘O’ gauge type Vlll # 1687 engine made in 1937. I am missing one of the three brass/copper knobs ( I do not know what they are called) there are three of them in a row midway on the top of the engine. If someone knows what they are called I would appreciate it so I can order them from ------? Thats my next question, where to order the parts. Is there a place to get a diagram of prewar engines ect? Thanks, jcolonbc