making a request for information

Greetings all from a land down under (Adelaide South Australia)
I am seeking help to work out a problem that has arisen here in Australia with the VH register
It all revolves around the Dash-8 aircraft
I will run through how I understand the situation and then you folk that are in the know can come in and clean up the mess and set me straight
In the first instance the Dash-8’s were produced by DHC Canada. Boeing then purchased the company which they (Boeing) then on sold to Bombardier (how am I going)
My question to you learned folk is does any on out there have any information as to how serial numbers tie in with the various manufacturers and the reason for this question is that our regulator (CASA) has decided that DHC Canada should now be shown as De Havilland Inc
It is my understanding that once a con plate is attached to an aircraft it cannot be changed
So if there are any of you out there that may have access to photograph a con plate on a Dash-8 I would be interested in what it says
regards
GeoffC