Hello, I have just bought a restored 1950s MB 146G with M nib from a seller in Germany. It is in lovely condition and writes nicely. However I think I would prefer a F or EF nib. The pen is apparently all original. Would it be a shame to change the original nib? Would it affect the value of the pen much? Would the nib still look just as nice after modification? (I would use someone like Mike it Work) Alternately I have looked online for a F or EF 1950s nib to swap it out but see none advertised. Are they rare? How much would I expect to pay if I can find one? Thank you, Paul Julian New Zealand