How do I open a 40 year old Chubb, Mosler & Taylor Class 2 Safe that
has suddenly forgot how to open after the combination has been dialed?

Hi old-ga,

I found this reference to Class 2 safes, from a usenet archived in
reference to safes and vaults.

http://yarchive.net/security/vaults_and_safes.html

"All Group II safe locks, by definition, can be manipulated.  Group I
locks,
which are mostly sold to the government, are not susceptible to
manipulation.
(And Group I R are also proof against radiological attack - i.e., they
have
plastic wheels so they can't be X-rayed.)

I believe the reason for this is that the manufacturers want the
locksmith to
be able to open the (group II commercial) safe if the combination is
lost, or
if someone messes up trying to change the combination.  Manipulating
it open
is cheaper than drilling it.  The government, on the other hand,
doesn't care
if someone gets in to the safe *provided they leave evidence they have
done
so*.  If the safe is drilled, blown, etc., then they know that someone
has the
secrets that were stored therein, and can take appropriate measures. 
What they
don't want is someone to be able to manipulate the safe open, copy the
secret
material, and then close it up leaving no evidence of tampering."

tlspiegel
Google Answers Researcher

Question:
Did you dial your first number clockwise or anti-clockwise?
Option1:
Begin the dial procedure anti-clockwise.
Option2:
This will take patience and several attempts...as you dial each
number, stop a half number in front it. If this doesn't work, dial a
half number behind.
Option3:
Call the Locksmith.

ziv