A German ligature that originally stood for 'sz', but can be transliterated as 'ss'. It is never found in Swiss German. It looks like a B, but sounds like an S. Compare to the boring language known as English, which only has the ligatures Ã and Å, which are rarely used.
The only other flour used in traditional pumpernickel is wheat flour, which is used as an ingredient in the sourdough starter, a pre-fermented flour, water and yeast mixture that combines with the rye flour to hold the bread together.
You can use basically any kind of flour you want. Bread is made with all sorts of flour, soft wheat, hard wheat, buck, malt, corn, rye... As long as you mix: any kind of wheat. water or milk. any kind of raising agent (yeast, sodium bicarbonate, baking powder, etc.) some salt.