Hi Bill,
My pump was leaking from that cover and I'm pretty sure no one ever removed it. I think the gasket just hardened up over time. The leak had bathed the side of the engine with oil and was causing quite a mess on the floor of the garage.
As a temporary measure, I cleaned it and applied a little silicone until I ordered a new gasket and I'll install it next time I have the manifold off. I did have to remove the SOV to remove the cover but i was in the process of changing all the o-rings over to Viton so I had the valve off anyway.
By the way, you're pump looks like this:
The pump in your picture is from a '95 and earlier OM606/603. The gasket looks the same though and appears to have the same part number.
I have an OM603 pump like the one in the picture sitting here and I can measure the screw for you later today.