Most round vault doors use a bolt pattern that includes bolts that are vertical and horizontal, or 12:00/3:00/6:00/9:00. However there are a few where the pattern has been rotated by a half-bolt; using the clock analogy, instead of one at 12:00 there are two, at 12:15 and 11:45 (for a 24-bolt door), and so on.
While these are not rare, they are at least unusual. The only maker who seems to have done this a lot is Herring-Hall-Marvin though they made plenty of “conventional-pattern” doors as well. Fichet, Tann, Lips, and even Mosler built some doors with the offset pattern; probably other makers too.
I don’t see any particular advantage for one over the other. With the offset pattern you’d need friction-reducing mechanisms on every bolt; see for example the separate thread “Hollar Round Door Vaults” (http://www.antique-locks.com/showthread.php/991-Hollar-Round-Door-Vaults?highlight=bolt+bearing). With the straight-up pattern this is a moot point for 2 of the bolts but they are likely to still scrape a little and lose some of their glamor :-). It may have been a simple matter of convenience so that the operating shaft was at 3:00 (or 9:00), as can be seen in the first and last images below.
Here is a small gallery of offset doors, most of which have appeared in other threads:
As always, comments/observations are welcome.
