I inadvertently selected "save as new version" from the system menu.

Is it sufficient to quit and rename the resulting files back to what
they were?  Inspection of SystemDictionary>>saveAsNewVersion suggests
it is.

By the way, this method had slightly surprising behavior.  I'm running
a 3.2 image, but also have a 3.4 image in the same directory.  When I
saved as new version, it used version 3.5.
FileDirectory>>nextNameFor:extension:  implements this behavior (it
finds the highest version number in the directory and adds 1), but to
me it makes more sense to bump the current image version number by 1
and complain if there's a conflict with an existing file.