Hah!! A subject up my alley...
If you asked me, most if not all 'sirim' stickered helmets are not safety prooved. Reasons, there are syndicates out there printing 'sirim approved stickers'...and every helmet manufacturer, local, Thai, korean, etc...seem to get their models stickered...making that a problem telling which from which...haha
But not to worry as even if your helmet did come with the 'original' sirim sticker, it may still not fall under International Safety Standards. I guess its safe to say that helmets that carry these stickers/tags are recognised internationally hence higher standards of safety:
USIS, DOT, SNELL - American
ACU - European, British
JIS, MFJ - Japanese
For most of the better helmets, you will find the factory approved 'seal' sticthed under the padding/cushion along with the size, date of manufacture and sometimes even with the tester's name.
"Comfort has several factors. For example, the material that makes up the motorcycle helmet's liner should feel comfortable against the skin. The internal padding of the helmet should act as a comfortable cushion between the head and the helmet internals, and the liner shape should perfectly match your head shape. The perfect helmet would be so comfortable that the rider would forget that it’s there."
The more notable brands are : Arai, Shoei, Nolan, Bell, AGV, Shark, Scorpion