That's not even the full Win32/16 style. That first line should be:

    static LRESULT WINAPI MCIWndProc16(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)

And even then MS couldn't decide whether to use message (MSG struct), Msg (SendMessage), uMsg (WindowProc) for the second variable name. Sometimes they would use hwnd as well. I remember it all being very, very confusing when I was learning to program because it was inconsistent in so many ways.

In a semi-related note, Raymond Chen's blog (1) is great for diving into the history of the Windows API and its many quirks and gotchas.

[1] https://blogs.msdn.microsoft.com/oldnewthing/