There is a delightful blog, by a lady called Chris Laning, devoted virtually entirely to medieval rosaries. It is a mine of useful information. She hasn't posted much recently, the reason being that she has been producing a monograph on the subject. I suggest you take a look at her blog, and her monograph (which I intend to buy).
I'm not really concerned about the "Catholicity" of her blog, but I do believe she loves the rosary and has done much to promote it, which can't be bad.