I have some 125 asa Orwo of that vintage that processes nice and clean
in Rodinal, also some 400 asa version that has a high base fog.
Chances are what you have will be as good as new, try it.

You've got the right idea -- test it, as you would any completely new
film.  The best result?  You got a bunch of (presumably inexpensive)
very fine grained slow film that will work just like new (highly
probable, if it's been refrigerated).  The worst?  It's all badly
fogged, and you have a bunch of film you can donate to local photography
instructors and the like for practicing loading daylight tanks.

Most likely, given what you say about prior storage, is somewhere near
best case.  I wouldn't change development time, but I would do a
ring-around test to establish correct EI; some folks have noted a slight
to severe reduction in sensitivity of old film, though film that was
already ISO 25 and refrigerated is unlikely to show that failure.  Once
you have the EI, you can make a good estimate from that roll of the
correction needed, if any, to development time and proceed from there.

FWIW, this is (IIRC) the same film company now marketing film as Efke,
and the ISO 25 is supposed to be orthopanchromatic -- that is, it is
sensitive to red, but less so than most panchro films.  That means,
among other things, that it loses more speed under tungsten light than
Pan F would.  Best to do your testing with natural outdoor light, and
throw in a red object here or there to check if this old Orwo is the
same as modern Efke 25.  If shooting with tungsten light, you'll
probably have to derate by 1/2 to 1 stop.

"Chris Loffredo" <me@privacy.net>

Take a roll of pictures and see if you like the results.  The film
may be a bit 'off', but then you may like the effect.

The film should be OK.  Slow film keeps much better than fast film.

Sometimes the response (H-D) curve changes with time; often shadow
speed is lost.  Take pictures of an evenly lit grey (or white) card
at -5 to +5 stops under/over the metered exposure.  Compare to the results
to those from your normal film & developer.

The worst case is bad fog and extreme loss of speed.  Often there is a
slight loss of speed.  Fog is minimized if the film has been refrigerated,
but it still may happen.  I have some Ektachrome and some Verichrome Pan
that expired in 1989.  They have been kept near or below freezing since they
were bought, and they work fine.

  There are slow changes in the emulsion with time. They
are a continuing of the "ripening" the emulsion undergoes as
part of its manufacture. The common result is fog. Emulsions
contain both anti-foggants and anti-ripening chemicals to
extend the life. Storage at low temperatures retards the
effect. Freezing film just about stops it. In general, the
slower the film the more stable it is so this should be very
stable film. Cosmic rays also cause some accumulation of
fog, but they affect mostly fast films and it takes years
for this effect to become significant.
  The chances are this film will still perform well. About
the only thing you can do is to shoot some of it and see how
foggy it is. Anti-foggants in the developer can make the
highlights clear but do so at the expense of speed, they
really do not get rid of the fog. You must increase exposure
with the anti-foggant but you must increase exposure anyway
to push the shadows above the fog, so the main effect of the
anti-foggant is the lower the overall density a little.
Paper is different because its important for the highlights
to be clear, but for film increasing printing exposure will
overcome a reasonable amount of fog.
  Please report back on this stuff and let us know what you
find. ORWO supposedly used older Agfa formulations. Agfa
film and paper was very stable so there is a good chance
this stuff will be also.

First report (Orwo NP 15 expired 1991 - apparently kept rerigerated, and
Ilford FP4 classic - no date and apparently no special treatment),

Not very scientific, but I developed my test shots and (based just on
observing the negatives):
Clear & out of frame areas seem perfectly transparent.
Exposure at ISO 25 & 125 seem right on.

Apparently the films really are o.k.
If any problems show up in printing I'll drop a line...

Chris