At the first glance, the coin (CII) looks cast due,among others, to the crack with rounded edges which can be an evidence of lack of metal during casting or a miscast original crack. It would be interesting to see the edge of the coin where it seems broken (9 o'clock).
In the other hand as Victor says, first it is difficult to judge only on a picture and two, a silvered look can have multiple origins. I have two folles that are looking like billon antoninian including the parts where they are corroded despite the fact that none them is known to have been struck with such a material.
So, I am very interested in reading the article you mention.
(https://i21.servimg.com/u/f21/15/86/03/61/bi47810.jpg)
(https://i21.servimg.com/u/f21/15/86/03/61/bi47910.jpg)