Casts? I don't think so. The styles don't look quite right to my semi/untrained eye. Casts should replicate the style of the originals used as masters. Struck fakes? I would be interested in hearing the opinions of our late Roman specialists.
They seem to appear very "white" colored and not the traditional bronze brown color that I'm used to seeing... but I'm not terribly experienced. Some have some pitting, but I'm not sure if that would be from casting or simply age. And some look like they are stuck. Just sharing my amateur thoughts and hope to hear from others to learn more.
They look okay to me. I think the off color is just bad photo processing. Notice the verdigris on the reverse of this coin? That's pretty hard to fake. And the color looks like whoever processed the photo reduced the saturation quite a bit Some of the Constantine IIs further down the page have some really neat obverse portraits.
I have no real opinion concerning the authenticity of the these coins, but I think @gsimonel is correct about the images being over saturated.
All of them are good and most in VF condition. The pitting alternating with the glossy surface is most likely the result chemical cleaning with a strong acidic substance. Most also look to have developed a post-cleaning patina so the cleaning was likely done long time ago. Seems like someone is selling his late roman collection.
+1 Casting bubbles are usually pretty round, corrosion tends to have sharp edges. These all look fine to me.
I think they are genuine, just poorly photographed. They may have been cleaned with electrolysis or acid solutions (it's hard to say).
I bought this coin a few years ago before knowing what more modern silvering looks like. This coin looks to have been relivered in recent times. It was apperently quite a common practice in the 19th Century.
Interesting, i wonder what happens when you apply modern silvering techniques over verdigris? Does it not take?