Before the Flag of the United States was changed to the "Commonwealth Flag", did the flag only have 49 Stars on it?
(Since Hawaii was not admitted to the Union until 1960).

That's a good point... probably? I'll bet Hawaii is having a great time over there during those 300 years.

While we're on this subject, what exactly is the commonwealth flag?

It's the US flag you see in Fallout games. The stars in a circle? I'd post a wiki link, but for once I'd like to see a lore forum thread not flattened by it.

Van Buren is the only game that had details about the new administrative division. While it's no longer entirely canon, according to JE Sawyer (lead designer of VB), Hawaii
was a state in the Southwest Commonwealth.

Of course, we don't know when exactly the Commonwealths were established. The Virgo II flag in the Museum of Technology in FO3 uses this design, so according to the Fallout 3 canon it was as early as the 1960s (according to Van Buren it was early 21st century).


See:
http://fallout.wikia.com/wiki/United_States_of_America

Would the "Commonwealth Flag" on the Virgo Lander, perhaps be an anachronism...or is it simply that the authors had a poor understanding of Fallout lore?

Or simply they did not consider Van Buren canon and introduced the Commonwealths earlier in the timeline than VB did. Actually, the Van Buren devs wanted it to be 21st century, but didn't even write it in the actual design documents, since it wasn't relevant to the design of the actual locations, so the only actual mention is from JE Sawyer's (who was Van Buren's lead designer) Fallout PnP.