I didn't know that there were once pinball machines without flippers on the side, but Arnold has a couple on display from the early 1930s. I even found The Wiggler, a machine I inserted many coins into in the basement of my college dorm (I became so proficient, I was known to sit backwards on the glass and still rack up free games).
Arnold isn't getting rich running the place, which doesn't charge admission, is staffed by volunteers and gives proceeds to charity. But if you have a few bucks left after you're out of quarters, he accepts donations to keep the place running. Take a look at photos of the Pinball Hall Of Fame's current inventory
here.