Yes, Your are right. Thry SCC4 only we can find whether client is open or closed.
In Your Screen shot, it shows as open - Automatic recordings of changes.mean its open to do changes.
If client was closed below options were used.
No changes allowed.
Cross client object changes - 3 No changes to repository and cross client customizing objects
Protection client copier and comparison tool - L protection Level 2 no overwriting no external availability.
CATT and ECatt Restrictions - eCATT and CATT not allowed.
Even SE06 and Se03 also we can find it.