Well, thats a 1275 all right, but that almost looks like something someone made. Thats a blanking plate to cover the hole for a mechanical fuel pump. I've never seen anything like it. Without an oil separator, it will spew quite a bit of oil out that pipe
Look at the schematics on Moss's site for the 1275 and look at the timing cover. There should be a cylinder about 4" long and 2" in diameter attached to the front. That's the breather. It should have a 1/2" hose going to a Y connector and then to the carbs. If its not there, then did someone fit a timing cover without one and try to add one somewhere else? I've never seen a gray block, but they could have painted it when they had it down. Can you post some more picks a little farther back so we can see the rest of the the motor, particularly the timing cover and carb setup. It should have a spin on filter, not a replaceable cartridge type.
You should note the residue on the heat shield and on the steering shaft. That looks like a heavy accumulation of old gas from a leaking carb, maybe from the flexible line going from the jet to the bowl, under the carbs. If that's leaking, fix it or carry a fire extinguisher, since a leaking exhaust gasket can ignite it. Fixing it is of course preferable.
Hows the oil level? Its not overfull is it?
-Michael