Gasket missing on brake fluid reservoir

[LarryM]

I recently discovered item #3 is missing on both my E28 and E24. I've owned both cars for many years and have done numerous brake system flushes yet have never noticed this before. I'm curious; is this a coincidence or does this part easily fall off and get lost?

https://www.realoem.com/bmw/enUS/showpa ... Id=34_0235

[Federico]

They do fall out. I once got a new one and later found the original stuck down there between the firewall and framerail.