https://bugs.winehq.org/show_bug.cgi?id=50623
--- Comment #8 from Esme Povirk madewokherd@gmail.com --- Bizhawk has an example of a COM interface that only has InterfaceType(IUnknown) and a GUID attribute. This can be observed by opening the path configuration dialog and browsing for a path.
MSDN says that ComVisible defaults to true. So it seems like an interface should be considered a COM interface if it (a) is public, (b) has a GUID attribute, and (c) does not have ComVisible(false).
I'm not sure if (b) is even a requirement, Framework might just generate a GUID for it.