The model 242 was built from 1950 to 1954 and, like every Montblanc writing instrument, came from the works in Hamburg. The marking on the cap end is to be read in two parts: the number identifies the model, the letter after it the nib width, F standing for a fine nib. The imprints 14 C and 585 on the nib denote the same material in two notations, namely 14 carat gold with a fineness of 585 parts per thousand; that was the firm's usual nib alloy in this period.
Value depends far less on age than on condition. What counts is a piston mechanism that runs freely and seals, a body free of cracks, undamaged cap rings and an undamaged nib with its iridium tip intact; it also matters whether nib and pen belong together. Replaced parts, nibs reground after the event and cracks in the material push the price down appreciably. A dependable assessment can therefore only come from examining the particular pen, not from the model number alone.