Authenticity of Our Sets

Ive really gotten into these sets.... I see alot of threads questioning authenticity of our sets online... What are the tell tale signs to look for??? These are mine Mclaren P1- Bought online from the Lego store- for sure authentic Ferrari SP3- Bought at Legoland in Florida- for sure authentic Lambo Sian- Bought on eBay-- Not 100% sure but looks solid and the seller has great history Bugatti- Bought on eBay-- Not 100% sure but looks solid and the seller also has great history Porsche- Landing...