Funny you mention the Union Jack, I actually ordered a AMQ union jack from Yoox 2 weeks ago but sent it back because it had some damages. It was a 100% modal scarf thus didnt look anything like yours aswell
. AMQ basically calls every scarf thats inspired by the British flag an Union Jack...
Back to your scarf: the wrinkles (not sure if that's the correct English word, the lines formed by folding the scarf) to me indicate that it is indeed a silk scarf.
The skull scarves are basically the only scarves that are being counterfeited (and have been for a while with a few exceptions like the Damien Hirst scarves), which makes buying a used skull scarves always somewhat of a gamble. Flaws are mostly seen in the tag, the printed logo (though not every scarves has it) and the edges. Especially earlier and still the cheaper counterfeits have major flaws in the printed logo, while yours is absolutely spot on perfect. I also don't see a reason for a counterfeiter to use a different (probably more expensive) way of manufacturing a counterfeit scarf. I'm fairly certain (~85-90%) that your scarf is a genuine one. Allthough this forum isn't as active as it once was:
maybe someone else can confirm .