Crankcase breather oil drain hole

Can anyone please tell me which models have the oil drain hole forward of the crankcase breather. Bike 75 R90S

Snowbum indicates it's not on the /5 models. See description for #22 on this page:

https://bmwmotorcycletech.info/oilsketch.htm

At the bottom of the page, he shows a cutaway of what the hole in the casting looks like.

That said, I thought it started with the /7s. In fact on an Airheads email list, he says that it was incorporated "in 1978" but he doesn't mention calendar or model year. On my /7, the cover for the breather hangs over this cavity in the engine casting. The oil mist then routes through a tunnel within the casting. I then have a black vent hose that connects to an outlet up near the starter and it routes back to the right hand carb into tube.

In my limited understanding I'm not sure if it remained in the Airhead motor through the end of production.

-- update -- Look in the above link near the bottom in the section titled "Breather System". Snowbum says that castings from 1977 or 1978 have the drain back hole.

I have an R90/6, built 01/75, and my engine does not have one.

Crankcase breather drain

Thanks. I saw the Snowbum article. I believe both illustrations are of the later /7's & up breather systems. Now I don't have to be concerned with taking my bike apart & trying to clean out a hole that isn't there.