It looks like a mid 50ies goldcapped Constellation ref 2852 with calibre 501 or 503 inside. Looks to be in good shape even if the dial has had it's fair share of moisture. This doesn't mean though that the movement should be bad. Have the case cleaned and the movement serviced and you should be good to go.
There are a few Australian members here, that ought to be able to direct you to a suitable watchmaker who can help you
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