I'm obliged to mention that identifont is powered by Common Lisp.

LTC Twentieth Century looks a lot like Futura.

Yes, compare the two and it's clear that LTC Twentieth Century (http://www.identifont.com/show?HVQ) is a rip off of Futura (http://www.identifont.com/find?font=futura&q=Go) (pointy angles on AMVW, no tail on the j, tall ascenders, backwards-S shaped ?, etc etc). The only significant differences I can see are in the less-used characters: LTC has a flat base on the ₤ and Futura a curly base; LTC has a supremely hideous Ø.

So Simon, are you sure it's not Futura? Futura is much better known and comes as standard with Mac OS X, so it's much more likely to be that.

You're right; it could quite easily have been Futura. I think I jumped to the conclusion that it wasn't because the first Futura-alike I looked at on that site was PL Futura Maxi, which lacks the backwards-S question mark, so I assumed that was a point of distinction between Twentieth Century and Futura. But all the other Futuras on there do have that question mark, so yes, it could perfectly well have been one of those instead.

In fact, yes, it's definitely a Futura rather than a Twentieth Century: the TCs both have a Q whose tail doesn't go below the baseline, whereas this font's does. On the other hand, it's not the Futura you link to there either, because that one has a J which goes below the baseline, and this font doesn't. So it looks to be either Futura (BT) or Futura Serie BQ. I can't see any clear points of distinction between those two, but on the basis of general weight I'd guess it's the former.

I can see some differences in those examples: the acute, grave, and circumflex accents have horizontal ends in the Bitstream version, but perpendicular ones in the Berthold version. This may not be of much help.

I'll keep an eye out for any accents that might crop up in the text, but I don't remember having seen any so far, so it may not help. Still, it's not terribly important.