Another Standard B question.

[gramophoneshane]

While working on the standard B I just got, I noticed that the back edge of the bedplate has 3 holes. As I'm waiting for a case to arrive from the US, I'm not sure if the middle hole is a screw hole, or for some other purpose. I can't remember the Standard A that I had years ago, having an extra hole- only the 4 corner screw holes to ancor the bedplate to the case. Then again, maybe I just don't remember it having one too.
Is it supposed to be there, and what was it for if not a screw? The only other thing I could think of is something to do with mounting a fireside size horn and crane perhaps. Can anyone enlighten me

[Don IV]

For what it's worth, the Standard D has three screw holes.

[gramophoneshane]

Thanks Don. Now that I look closely at the px of the case I'm getting,I can just see a third hole, so it must be a screw hole.