One thing that I have learned during my recent visit to Money Museum at Sasana Kijang is that there was a series of specimen banknotes printed under the Central Bank of Malaya (Bank Negara Tanah Melayu) in 1950s by a British printer but were never confirmed and released.
If we can recall the history, the authority to issue currencies is vested under the The Central Bank of Malaya Ordinance 1958, which formed the Central Bank of Malaya (Bank Negara Tanah Melayu) in January 1959. However, the Board of Commissioners of Currency Malaya and British Borneo continued to issue currencies until June 1967.
Specimen banknote under Bank Negara Tanah Melayu
There are other specimens banknotes displayed. For instance the first series of RM100 not was printed without the portrait of DYMM Yang Di-Pertuan Agong. Others were printed adopting the similar concept or design from the Board of Commissioners of Currency Malaya and British Borneo. But none of them were successfully gone through it.