I could be mistaken, but the information below is directly from groundspeak.
So I think '?' cache means puzzle not unknown container.

 I do know that some caches have been changing recently so I think reviewers
are adjusting them as they are found. I had one of mine changed to a multi
instead of traditional just by emailing an approver. I think if you have
found some that should be '?' you could email one of the reviewers and see
if it could get corrected.

Mystery or puzzle caches
The "catch-all" of cache types, this form of cache can involve complicated
puzzles you will first need to solve to determine the coordinates. The only
commonality of this cache type is that the coordinates listed are not of the
actual cache location but a general reference point, such as a nearby
parking location. Due to the increasing creativity of geocaching this
becomes the staging ground for new and unique challenges.


-----Original Message-----
From: az-geocaching-bounces@listserv.azgeocaching.com
[mailto:az-geocaching-bounces@listserv.azgeocaching.com]On Behalf Of Koch,
Dan
Sent: Wednesday, December 29, 2004 9:34 AM
To: 'listserv@azgeocaching.com'
Subject: RE: [Az-Geocaching] Puzzle (no, not Puz-Zel) caches


I did set up a pocket query to grab those caches that are designated with
the '?' cache-type, which is how I obtained this list, but it's the caches
that ARE puzzle caches but AREN'T indicated as such that are the problem.

It's usually older caches that aren't labeled as such because back in the
old days, puzzle caches weren't labeled as such and the '?' seemed to be
reserved for mystery containers.  These days, it seems that '?' means puzzle
much more often than it means mystery but there's no rules about what '?'
signifies.

And with the current rules for modifying caches, cache owners can't just go
in and change the cache type (like we used to) to make them easier to find
via query.

That being said, anyone know of any more puzzle caches that aren't labeled
as such?

Thanks!
LazyK - Dan