Red Onion Helm - Does it even exist?

[PaulusHamsteru]

there are 400 red onion helm drops reported on 16m quick ventures
100 on 4m ventures with retainers lower than 100 and 300 on 12m ventures with lvl 100 retainers

seems like odds are about 1:40.000 ventures to get it

Where do you check this?