Selecting which application opens a file with given creator/type codes (System 7) In System 7, when the user tries to open a document of a type which multiple installed applications can open*, it pops up a dialog asking which one to use. After one is chosen, that application seems to always be used to open that type of file, by default (although it can be manually opened in the other application(s)).

How would a user bring this dialog back -- thereby allowing them to choose another default application? If it's not possible to bring back the dialog per se, how can the user change the default application?

* I'm not sure which of the type code or the creator code, or both, the Finder is using to determine the available apps and the default app to open the document. I know how to change type and creator codes using either ResEdit or -- since the System 7 I'm using is emulated on OS X -- using SetFile -c and -t from OS X. But, seemingly, the initial choice of default application makes the Finder behave a certain way for all files similar to the one double-clicked; it doesn't change the type and creator codes.
I don't have a System 7 Mac to test this on and my memory is a bit hazy - only partly helped by web searches - but I think you want to go to the Mac OS Easy Open control panel and click Delete Preferences.

If you don't have this control panel or something similar then you could also try deleting any likely-looking preference files in the Preferences folder in your System Folder, then restarting; or deleting the hidden Desktop DB and Desktop DF files from the root of the disk, then restarting if it's the startup disk, or ejecting and reinserting it if not. 

Note that all these methods (if successful) will delete all application associations for unknown files, and deleting the desktop files will delete or reset a load of other stuff such as window view settings and possibly Finder comments.