I have the same kettle I use with an extender as a WSM. Sears had an "economy" kettle that was a 3 vent bar-b-kettle. There are just a few subtle differences. 1. All black wheels. 2. No information stamped on vents. 3. The original coal grate was actually a porcelined pan with a thin grate above it. The idea was after a cook you could just empty the pan. The grate did not last very long on most, so if you are lucky to find one with a little use on it the original coal grate is probably gone.
I too found mind as a "trash" kettle. I cleaned mine up and bolted on the leg attachments to the kettle and then bolted on the lid handle. It cooks up a storm now. Had it for almost ten years.