I have a vintage MONTBLANC Masterpiece fountain pen with a 14k gold nib and a rolled gold cap. It has three markings on it's end, that read 644 N, F4 and JB. What do these markings mean? The body is kinda green and slightly transparent. I do not know much about fountain pens and would like to know the year in which it was made and the value and what the green color of the body is made of ? If i sell it how much can i get for it. It is is good condition but not in mint condition. Any info would be of great help. Thanks a lot.