The word “Mahzor,” familiar to most Jews as the term used for the prayer book for the High Holidays, means “cycle.” It can therefore be used to describe a book containing any liturgical cycle. Sometimes the term was also used to describe a text created in codex = book form, as opposed to a traditional Jewish scroll.  

The Bamberg Mahzor, completed in Bamberg, Germany, in 1279, includes prayers for the entire year according to Ashkenazi custom. It is distinguished by its Ashkenazi script and the style of its decoration. 

The open gate on this page illustrates the prayer within it, a formulation of the first blessing before the morning Shema, used only on Rosh Hashana, that speaks of God opening the gates of mercy to us as we are judged.  

In the margins, a later user of the mahzor, probably a cantor, adds prayers for the holiday that were not included in the original manuscript (they may not yet have existed, or they may not have been part of the local Bamberg custom).