What the W

I acquired this 318 2 barrel engine that came from a 1968 Chysler Imperial or 300. It has this W on the intake it and I can't determine its significance if any. I also included serial numbers if anyone can tell anything interesting about it as I have heard some 318s were special equipped with forged steel cranks and possibly bigger valves. Serial numbers start with PM318R. W=Windsor Ont.? 20211211_114827.jpg.

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