Something, very very old.
Even the 3rd party tools largely limit you to 8 or 9i instances.
Hopefully you have a migration/upgrade plan to rid yourself of any 734 instances of Oracle
Oracle 7? Wow! Super old...
Oracle 8 included sqlplusw.exe which was a Windows based version of SQL*Plus. That can connect to Oracle 7.
SQL Developer won't do it. Even Project Raptor (the first version of SQL Dev) could only connect to Oracle 9 and higher.
Out of curiosity, what OS is this Oracle 7 database running on?
The 'official' word of the latest Oracle SQL Developer (4.1) says that it is certified for Oracle 10g and later. Does anyone know what other Windows graphical UI can be used (as an IDE) to work on an Oracle7 database?
You're about a week late for an April fool's gag but that was still pretty good.
Seriously - I suggest that the most IMPORTANT contribution you could make to the 'museum' that has that 'ancient artifact' would be to get whatever useful data still remains out of that version and into a more useful form.
Maybe a set of Excel files? (oh sorry - that's a week late too!).
Get the data out of that version while you still can or the lack of a GUI interface will be the LEAST of your problems.
The few data recovery firms that could still salvage that data for you will be VERY expensive should you need to use them.