Unusual 1920's Mont Blanc Pencils

I found these two very unusual Mont Blanc Pencils some years ago. I am sure that they date from the 1920's. I have tried researching them but up to now, I have not been able to gather much information about them. Does anyone out there have any clues as to why they were made so large, were they for shop window display? Its the only reason I can think of. Here are some facts about these pencils: The larger one has number 16 on the side just below the star and the smaller one has number 13 on it, they are both marked Mont Blanc. One is 30 cm long and the other is 18 cm long. They are rotary pencils and are both in working order, they are made of vulcanised rubber.