welcome!
i haven't seen the condition of your knife.
(and will not be able to access your picture).
so i'll just address rusting.
in general, once rust develops over
the zinc phosphate coating,
the eroded finishing can't be saved
since its been eaten away.
so corroded areas are in danger
of developing rust spots and possibly
the dreaded pits too.
first thing to do is to wash and scrub
down with a fine tooth brush.
you may use dish washing soap.
you only want to clean up the blade.
so be careful not to let water run
anywhere above the guard .
pour some hot water over the blade
and let the heat evaporate the remaining moisture. air dry in the sun.
inspect how much of the original finishing is left.
then decide if its worth saving.
the zinc phosphate coating.
at this point its worth to note
that any messing around with
the blade surface will depreciate the
collectability of the knife in the eyes of a collector.
if you intend on use. then by all means
proceed to maintain it as a using knife.
there are only two ways to completely
remove rust. one is through abrasion
action and the other chemical corrosion.
it becomes a matter of personal preference of just how ciean a surface
one wants to achieve.
only remember that any bare metal surface will begin to rust once more
so lets look at applying a protective coating. you may use generic oils .
or other forms of solutions use in aftercare of firearms. i hope this gives you some diection in your approach
in dealing with your new found knife.