These are the earlier tanks used with a JOBO processor.
It ... comes ready with a hole in the plastic cap so when developing C41 the 'gassing' it makes ... does not make it leak when pressure builds up.
These Jobo Series 1000/2000 tanks were introduced years before their rotary processors. But already the predecessor series were intended for inversion, and thus had to be tight.
None of my Series 1000/2000 tanks has a cap lid with a hole.
This of course would have made them useless for inversion processing.
The first drums, solely intended for rotary processing, seemingly had no hole in the lid for gas exchange.
Then the drum lids got a central hole.
But in the manual of the 3rd version, with upgraded cap with floating dipstick, the photo still shows caps without hole whereas this version actually got that hole too...
As indicated, the number of series with subversions makes it all confusing.