First H-D Electric Leg?

Just when you think you've seen it allThis 53 H-D was on Ebay 2 years ago. The seller didn't mention it's most unique feature. There were other photos of the bike's engine but I'm highlighting the starter set up. It would be cool to restore it to working condition. That's a Police issue oil tank behind the large starter gear. How about them horns out front? Must have been some bike in it's day.That's no saddle bag. It's one hell of a battery box. The size and shape of the box means it held an old car battery which indicates that this mod was old.The spring must take some of the shock out of the motor's initial kick. Another view of it. Those are oil lines are crossing under the shaft.I'm guessing that's a relay switch.Once again, a backyard builder was doing H-D's R&D.OK Guys, Here's today's trivial question: What year did H-D first come out with an electric starter? (Sorry), Lewy K, Noot, Irish Rich, Dr, Sprocket, and Knuckle Buster can comment but, are all banned from the question.