Pelikan’s convention of choosing descriptive model numbers has, in general, been one that is easy to follow. A fair bit of information is conveyed with just a single letter and a few numbers. A ‘P’ indicates a cartridge pen whereas an ‘M’ denotes a fountain pen. The first number in the model is the series number indicating models of roughly the same size and style. If the model number ends in a ‘5,’ the pen has rhodium trim and if it ends in a ‘0,’ this usually, but not always, indicates gold-colored furniture. This code, while simplistic, is overall well thought out and effective. How then do we explain a pen that defies these conventions? In a previous post I addressed the case of the M201, a clear demonstrator which turned out to be an M2oo is all respects, just made in a limited run for the Japanese market. I also discussed the M150/481 which has proven very confusing to collectors over the years as it combines numbers from two separate models, a short-lived convention used in the mid-80’s. With these precedents in place, it should come as no surprise then that you can regularly find pens for sale in certain markets branded with the designation M151. If you own one of these, rest assured that it is a legitimately produced model from Pelikan (link is in Italian).