Sorry to dredge up an old topic, but I thought I would weigh in here. I have a Bumerang myself that I bought new back in the late 80's as I recall. These were made back in the day when all we had was depth weights. There is a counter that is supposed to help you return to the same depth and is also resettable. One lever releases the reel stop. The second lever is a "twitching" lever that moves the rod up and down to create a jigging effect. The handle has a removeable plug and is hollow to store tackle.
Mine has a curved rod, but my guess is that it was straight at one time and got the curve from being under tension.