Variable fonts

Hello,
I am currently using the multiple master feature of freetype library to
support the variable fonts. There is an issue that I am facing currently.
For an example, consider that I am making letter "A" bold using the weight
axis but in my system I want to be able to uniquely identify the default
normal "A" and the bold "A" but since the unicode id will be same for both
normal "A" and bold "A", Is freetype library providing any other identifier
which can uniquely identify them?

Thank You,
Tulsi Amin