How to indentify the canadian pressings

I have been taking a closer look at the canadian pressings of the early Ramones albums because I have seen a lot of different versions. The thing is that canadian WEA had a system in the 70's and 80's where they printed a letter on the label that indicated witch pressing plant that had made the record. This means there could be three or maybe four versions of an album, all released at the same time! For example there are pressings of End of the Century with pressing code C, Q and I.
After some research I have identified the following pressing plants:

Code: C
The Ontario plant Don Mills that was running between 1971 and around 1989. WEA Canada used the label code "C" for this plant.

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Code: Q
Quality Records Ltd. Starting in the late 70's the WEA label code for this plant was "Q".

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Code: I
I can't find any information about the canadian pressing plant that used the code "I". Anybody who knows?

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Code: CR
Records pressed by Cinram at Toronto. This vinyl plant was opened in 1979 and closed at 1991. WEA Canada's label code for this plant was "CR" and "CI".

To make it even more difficult to get the whole picture there are also canadian pressings without the code.
As far as I know all singles on canadian WEA/Sire are pressed at Don Mills and have the "C" on the label. The exception is the Rock'n'Roll High School 45 that don't have any pressing code at all. You can see the singles here. It would be interesting to know if anyone out there have a single with another pressing code.
And if you can help me fill up the list of different canadian album pressings please let me know.
Thanks to ramones.fi for help with pictures!