I gather it’s their sidecar engine?? so maybe the plates have something to do with that although they don’t seem to be visible when the bike is assembled.
Not sure about the vacuum pump... looks more like a glorified catch tank, but that wouldn’t explain the gauge on the bottom of the tank. I recall seeing a photo of a twin with a vacuum pump installed, but don’t recall if it was Irving.
The drag racers in the US used vacuum setups... just plumbed into the exhaust to help retain oil. They discovered it also added a bit of hp. Then switched to vacuum pumps when the people against everything complained about the noise and mufflers meant plumbing into the exhaust wasn’t an option. You can still buy kits to plumb a breather into the exhaust on small aircraft. I don’t have any hands on experience with vacuum pumps, but I’d be cautious about sucking any of that precious oil mist out of the engine.