Model 50 crank oil seal. Where?

After splitting the crankcases to get to the crankshaft, I didn't notice there wasn't an oil seal on the sprocket side. But now I'm about to put the engine together, it dawned on me I was missing something: said oil seal...

However, I fail see where the oil seal should be. There just doesn't seem space for it.

It's a late alternator engine and -seen from the inside- there's a bearing, another bearing, an empty space (maybe the second bearing has shifted during splitting?) that seems too big for an oil seal and then the hole through which the crankshaft end goes. That's a close fit around the shaft.

In that hole, there's a slot in the bottom, going straight through. I first thought this might drain the oil, but it's going to the outside of the crankcase.

What am I missing?

Thanks in advance for thinking with me.

Tim