One thing to remember when operating an automatic bolt motor with the door open, is to always remove the crank handle. On the larger vault models, the handle could break an arm as it spins back. Given the close proximity of the little timer control handle to the overnight timer release, the hole may be so a pencil or pen could be used instead of your finger. Also the two different Burton models shown in "American Genius" are earlier pre-S&G versions. The one I worked on was, like yours, an S&G but a larger model. According to one catalog page they came in 4 sizes.