A 1940's M&P, coming from a guy in Austrailia, sounds like a Victory
model in 38 S&W. If that is what it is, and if it spent time in WW2
in Austrailia, then we are talking about a gun with some history,
involved in that history, in that part of the world.

In such a case, I think the condition of the gun reflects what it
went through, and I think it would be inappropriate to refinish it,
as it would lose a lot of what it went through. There are a number of
products that will kill and remove rust, without damaging any finish
that may be left. In this context, I would certainly clean it up, and
have any repairs made, if necessary, so that it is functioning properly.
Then I would keep it well oiled, and leave it alone.

Imagine, for a moment, walking into a military museum, and finding
that all the artifacts on display had been restored. I suspect that you
would wonder what you were doing in such a place.

Historically significant items are what they are, in large part because
they are historically significant. I think that is how they should be
maintained.

Mike Priwer