@windyr,
There were thousands and thousands of Madonnas painted in this style so there are probably tens of thousands of forgeries.
I'm no expert but something about your Madonna's feet bother me but that could be just because you didn't see her feet in most of the icons.
I'd most definitely get it appraised. Your local museum might be a big help.
Let us know what you find out. This is one of my favorite periods of art so I'll be curious to know what you've got!