MKA means Martin and King. They were the railway workshops in Melbourne (owned by Clyde Industries) who were contracted to assemble the first German CKD kits for Regent Motors, and later Volkswagen Australia. The new Volkswagen Australia company bought Martin and King in 1957.
http://www.clubvw.org.au/history002
It would have been an assembly number that Martin and King stamped on the panel when the car was being assembled in Melbourne.
Martin and King didn't begin assembly for VW until June 1954, so your car would have been assembled after that. However the component parts themselves were made in Germany and sent out here in crates. They could have been made many months beforehand.