1/- pale blue green punctured OS

I have recently acquired a block of 4 1/- pale blue green punctured OS and cancelled with cds Rabaul 22nd January 1922. On examination (I was so surprised to see the multiple I was more intent on checking the puncture to ensure it wasnt a forgery)the block is Die 2b not die 2 as catalogued at O11a. Die 2b was issued in Australia in December 1920 and the NWPI sheets were sent from Australia in 1921. It is therefore feasable that the issue should be Die 2b rather than Die 2. Interestingly all my singles of 113a are Die 2. Can any member confirm the position to me? Thanks in anticipation. If anyone wants to e-mail me my e-mail address is robertbenoist@hotmail.com