Does not seeing “Swiss” on a dial mean redial???

I wanted to pose this question to fellow members in the hope of gaining some knowledge to arm myself and others with for our future purchases and also protect us from uneducated or crafty dealers. So I have seen threads in the past where people have asked for advice on the authenticity of a dial and I have seen comments where people have said that the lack of a “swiss” or “swiss made” marking at 6 o’clock would make the dubious of the dials authenticity/originality. I have also seen many watches online from brands such as omega, Patek & Vacheron where no Swiss marking is present and the dial is supposedly completely genuine, some do the dealers I have seen offering these watches are very respectable ones who I would assume would have the experience and knowledge to know such things. Any opinions would be greatly appreciated, Cheers guys