The museum does not have an example of the original PFK overlay that was used on the versions of Unigraphics delivered before 1978.  Note that while it was never officially called UG0, if the version released in 1978 can be properly called UGI then theis previous version should have been called UG "zero".  Note that while the overlay looked similar to the UGI overlay, the biggest difference was that the two lower right had buttons were labled "Yes" and "No".  Whenever the system requestred that the user answer a simple Yes/No question, only these two buttons would light up.