It's a word with multiple meanings, though admittedly the one you mention is the most common modern one. Presumably, given that it's a journal and about medieva

It's a word with multiple meanings, though admittedly the one you mention is the most common modern one. Presumably, given that it's a journal and about medieval studies, it's a reference to speculum literature: https://en.wikipedia.org/wiki/Speculum_literature https://en.wikipedia.org/wiki/Speculum_literature