rear brake drum play

I'm replacing the speedo gearbox and rubber cush drives on my 74 Commando. I started to replace the rear wheel today and noticed that the rear brake drum/sprocket has a large amount of side to side play. The brake backing plate is locked in place but the drum/sprocket has a lot of movement.

Is this normal? Before I go through the trouble of getting the wheel installed with the new cush drives, I sure want to know if there is something else that I need to fix.

Thanks.