Greetings, I own a CG Conn French horn I purchased a few years back. It has a 4D marking on the top of the lead pipe and serial #336666. I have looked up information on the 4D and it indicates it is a single French Horn with optional slides of which I have a Eb. However, where I have questions is the picture of a 4D does not look like mine. I would like to attach picture for comparison, but I am new. It states the 4D was manufactured between 1929-1939 and the serial# indicates 1940. Were there different models of the 4D made?

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Also it had an 11 mouthpiece, not sure of brand, but I cannot hit the low notes. Remember I was primarily am a trumpet player, so what do you recommend I change too?