"unmanaged" generic parameter constraint in IL

When I compile the following code:

type Class1<'T when 'T : unmanaged> =
    class end

type Class2<'T> =
    class end

in IL it looks like this:

.class auto ansi serializable nested public Class1`1<T> extends [mscorlib]System.Object

.class auto ansi serializable nested public Class2`1<T> extends [mscorlib]System.Object

Is the unmanaged constraint saved somewhere? If so, where and how can I programatically obtain it?

In this question, I read it is somewhere in the "emdbedded signature file". What is that?