That looks like a 2/3 series oil seal and yours is an early engine. I have not taken an early engine to bits so cannot be sure, I think someone else will confirm this
If early engines just have "throwers" that would explain why you had an oil leak when you tipped the engine, Aprilias are like this as well. Again, you need someone with more experience than me to help here.
By the way, your workshop seems far too clean and empty, you need lots more projects ....