venetian mirrors

Lady who sold them said that the mirrors were Venetian, there are 2 of them exactly alike.  Both are beveled, the glass seems to be a smoky cracked look.  

Can anyone tell me how to know if they are really Venetian and how old they really may be as well as value. 

Any help is appreciated. 

After I establish a true value, I may sell as a set or individually.

Thanks

Good