Small world, I'm actually the one who sent that email. I have come across MANY of these with the eagle head (not always the same one) in different styles and none have been sterling even though many are falsely marked as such.
I don't claim to be an expert but I see a lot of Mexican jewelry and there seem to be 3 or 4 bracelet styles that were commonly falsely marked.
The one like in this thread, one that has abalone (usually) or other stone masks, I also have one in Sheen Obsidian, the abalone and enamel floral tension clasp bracelets and the ones that have 4-5 bar links with a pyramid link in between.
There are many more that don't use the eagle head, just 925 or sterling, but every one I have seen with the head and sterling/925 has been fake.
It is my belief that the eagle head stamp is an attempt to fool people into thinking they have an "eagle" marked piece so it is genuine. Lots of alpaca pieces are marked alpaca so the absence of it seems a bit deceptive.
There are also a lot of Mex pieces marked SS that are not sterling, I believe that too is an attempt to deceive, it looks like silver so people assume the SS must mean sterling.
I test ALL my Mexican jewelry now, there are a lot more fakes out there than people are aware of.