Of real benefit not just to numismatists but to medievalists who deal with material culture, economy, politics and more, are the three catalogues of Byzantine and medieval coins (including those of Ostrogoths, Vandals and Lombards, plus later coins from Thessalonica, Trebizond and Nicaea) by Warwick W. Wroth (see my delicious links on the right hand side). They are all now well out of copyright and you can at least read them via the Internet Archive which leads you to Google Books. They are allegedly available for download but I cannot seem to achieve this. I wonder if there is some residual rights problem as facsimiles of these volumes have also recently been published? However, you can at least consult them here. The quality of the reproduction is at least as good as the originals and so perfectly suitable for research purposes:
Last May, I gave a short cameo paper on the theme of identities in 11th century southern Italy. It revoles around two examples, one of the description of Duke Melo or Melus in William of Apulia’s poem in praise of Robert Guiscard (Book 1) and the second on the depiction of the Earth (tellus) in one of the Bari exultet rolls.