Old plate white and blue with golden decorations

Yes you are right
But it's strange no underline
Maybe that 'a' and the '12' can help ?
Unic mark that exists not underlined is C2 but you're right that one cannot be the right one because it's not ink printed

 

I have but I'm not sure I can add anything helpful. If this is older Haviland it's not a mark I'm familiar with. I would say it's European and definitely hand painted. The brush work and color palette leads me to believe French is more likely than English or German but that's a guess. I would date it as late 1800's. All of this, however, is just my humble opinion.
Don

 

@dgbjwc and @i need help

Thanks a lot for the info and time

 

Yeah