Not to put to fine a point on this but the hole doesn't seem to have a purpose as far as we can tell. Check out this thread and scroll down to the Swiss guy's post.

By the way, I have a M-B 320 First Aid Kit I would like to sell if any one is interested. I paid about $10 for it on eBay before I found a Crossfire kit. PM me if you would be interested. Shipping wouldn't be much Priority Mail. It's light.