This came to my attention recently when a person was postmarking his Panda postcards in the GPO. He was comparing the cancellation with the postcards made in Zoo Negara on the launch date.
Apparently the cancellation in the GPO has a missing cheek on the baby panda! The cancellation in Zoo Negara has a faint but visible cheek.
I confirmed this when I went home to check the postcards and covers that I made in Zoo Negara during the launch. Yes the difference is clearly visible.
This photo shows the difference. On the left of the picture is the postcard from Zoo Negara launch. On the right of the picture is the cancellation from the GPO. Notice the missing cheek?
Perhaps the cheek line broke off? Or could it be a different rubber stamp? Which variation do you have?
Here is a picture of the rubber stamp that might answer the questions: