The Royal Australian Mint has paid tribute to the Royal Australian Corps of Signals' centenary by unveiling a one-dollar coin with a hidden message.

The uncirculated coin - 50000 of which have been issued - honours a century of service in military communications and features a cryptic mystery in Morse and binary codes.

The Royal Australian Mint has paid tribute to the Royal Australian Corps of Signals’ centenary with a special one-dollar coin featuring a hidden message in its design.

The uncirculated coin - 50,000 of which have been issued - honours a century of service in military communications and features a cryptic mystery in Morse and binary codes.

Collectors and military enthusiasts are being challenged to decode its secrets.

Head of Corps Brigadier Deane Limmer said the coin captured the swift and sure century of service. Swift and sure is the English translation of the Latin motto Certa Cito, which emphasises the necessity for communicators to be quick and accurate in messaging.

“The design is fabulous, capturing our Corps’ Jimmy badge with the background of Morse through to current-day binary code,” Brigadier Limmer said.

The Mint had to consider copyright issues related to other symbols and avoid complications with intellectual property.

Australian Mint designer Adam Ball used a globe in the design, drawing inspiration from the badge.

“If I just got the badge and put it on the coin it wouldn't have fit because of the shape and style,” Mr Ball said.

He then considered what the organisation represented to create the final design.

With more than 100 coin designs under his belt, he said it was hard to pick a favourite.

“A few of them are competing for the favourite, but this is one of them,” Mr Ball said.

The design process began with an outline sketch of the theme followed by approval, then 3D production.

Brigadier Limmer said the Mint had a tradition of creating coins to commemorate historical events.

“One of their recent projects was a coin to celebrate the anniversary of the Australian Signals Directorate,” Brigadier Limmer said.

“The signals community is definitely aware of the new coin. I've seen many current and former signals personnel buy them.”

The coin can be purchased on the Royal Australian Mint website.