The 30, 31 and 32 belong to Montblanc's inexpensive third series and were intended as plain everyday and school pens. All three carry a steel nib; on the 31 and 32 it is also found gold-plated, on the 30 never. A gold nib is therefore not to be expected on these numbers, whatever the length of the barrel or the shape of the pen.
If the nib shows a crystalline, pimpled coating, that is crystallised ink residue and the beginnings of corrosion. It can only be removed very gently, and only with the nib taken right out: unscrew the pen at the middle, then push the nib and feed out of the section from the rear. The seals must not be damaged in the process, as they are brittle on pens of this age. Expect any gold plating to suffer during cleaning, or to come away altogether. If the coating does not interfere with writing, the better decision is usually to leave the nib untouched.