There was no quality control with the Canadian made at the Factory.
Harbour Lights would have to check them and if they spotted an imperfection, they would send it back to the manufacturer. Bill said many a time the Manufacturer would do nothing and send it right back to Harbour Lights. Painting defects was the big issue with the Canadian made. That is why Harbour Lights switched to Malaysia. I would imagine that cast imperfection past thru also.

Molds did not last forever. They were replaced after so many pulls. This may have been a mold defect before it was replaced with an other one. If this is the case maybe a few more of these defects are around.

To me it looks like some impurities were in the batch that did not allow the cold cast resin to pack tightly to form the correct texture. Maybe Resin from the previous pour or dirt fell in. If this were the case, there would be only one.

Harbour Lights would call this a defect and when it was first purchased it could have been sent back to Harbour Lights for a replacement. However, in our Waco world of collecting I think most of our collectors would value it as a variation.
I personally think it is a great find and it is always neat to have something different from the rest of the lighthouses.

Bob;
You may want to check and see if it was from a California mold. If it is the windows on the door will be irregular.
Check the picture on page 35 of the GreenBook
Also check it with your #147

I will have to check my two North Heads later.
One at home and other in storage.