First, I draw a circle of radius 30mm on the origin .After that I draw the next circle of radius 20mm and dimension it 129mm away from the bigger circle on the same y-axis. In the area between the circles, I draw a construction line 10mm away from the x-axis. I use that line to draw another line to connect the 2 circles, then mirror it along the x axis.
Next, I draw a rectangle 70mm by 10mm outside of the main shape and create a point on the center of the rectangle. I also created a point at the center of the middle region. Then, coincide the 2 points, the rectangle is in the center. To finish it off I add the 2 circle on both sides of the rectangle and the 2 polygons in the 2 big circles.
I add the 2 polygons in the circles and trim off the unwanted lines. Extrude the Main shape first by 10mm on both sides, then the smaller rectangle by 5mm on both sides.