Crankcase repair (53 Vincent restoration)

This is a picture of the bike just after I arrived back home Monday afternoon. Can you spot which part is missing?

On the other picture it is possible to see the oil trace from the street into the parking place.

I job colleague with family just happened to over take me about one hour after a started my 13,5 hour ride from Stockholm down to Travemünde. His wife took this picture.

I believe I'm listening for any sounds coming from the engine, looking in a rear mirror or checking what gear is engaged.

Interesting breather mod approach...