Caddy, it later emerged, had been a well-known dancing champion, nicknamed The Bondi Jitterbug, in the late 1930s. He was one of the first to shock the staid ballrooms of Sydney with the unashamedly erotic steps of the dance craze that had swept America - a combination of charleston, lindy hop and truckin' whose origins lay in the jazz clubs of Harlem.
But Caddy, who had moved with his family to Sydney from Melbourne in 1929 when he was 15, also was a keen amateur photographer whose work was well-known within camera club circles. Like his professional contemporary Max Dupain, Caddy was influenced heavily by the modernist style he'd seen in the New York-based Popular Photography magazine.
And, from 1936 until 1941 when he was enlisted in the Army, he spent most weekends down at the beach, photographing his friends who were members of a local gym.
Davies, however, knew none of this. The only information on the negatives were the dates each photograph had been taken.
Even Caddy's son, Paul, who had found the box when he was clearing out his father's flat in Maroubra after George's death in 1983, had not appreciated how precious the photographs were. He'd taken them with him to Tasmania and forgotten about them for two decades. Davies could see that George Caddy had been "an exceptional photographer, jaw-droppingly good". But who were his subjects? Where had they learned their acrobatic skills? What equipment had Caddy used? And why was there no record of any of Caddy's photographs after he went into the Army?
For example, there's one photograph showing two perfectly focused, somersaulting gymnasts frozen mid-air, with grains of sand glistening in the sun. Even today, using digital cameras, automatic flash and auto speed, it would be difficult to replicate. So how did Caddy manage it on October 4, 1936?
Davies and his colleagues began searching, detective-like, for clues. Fortunately the State Library was the best place to start.
Regina Sutton, the State Librarian, says Caddy's short but brilliant burst of creativity "would have remained unknown were it not for the Library's resources . . . Books, magazines, electoral rolls, telephone directories and [our] online catalogue all contributed."
The first breakthrough came when Davies found one of Caddy's photographs - a group tableau of seven men lifting five women - in the library's copy of Health And Physical Culture magazine, published on February 1, 1939 (three years after Caddy had taken it).
It illustrated an article by Wal Balmus, a professional strongman and keen beachobat. Balmus recommended sand gymnastics because it brings "young couples together to enjoy each other's company . . . minus mock modesty". Crucially, it identified the people as members of the Graham Gymnasium.
Colleagues at Waverley Library soon established that "Graham Men's Gymnastic Club" had been formed in Waverley in 1921. A story in the local paper, appealing for more information, struck gold - a reader who had kept an album of Caddy's beachobatic pictures, with the names of the gymnasts on the back of one print.
Bit by bit, the story of Caddy and his extraordinary record of Bondi beach life unfolded. A favourite subject was Valmae Maher, a North Bondi beauty who regularly appeared as a pinup in Truth magazine. On February 3, 1940 she posed provocatively for Caddy, lying in the sand wearing what locals called "a swoon suit" because of its peek-a-boo cut and lace-up panels.
Another 1940 photograph shows Caddy posing with the camera he used to take his beachobatic shots. To an expert like Davies, it's fascinating: a Voigtlander Bergheil plate camera with a wire frame viewfinder, flashlight attachment and roll-film back, producing 6x6 centimetre negatives.
Further research revealed details of Caddy's life even his son didn't know. Born in Melbourne in 1914, he was only 17 when his unemployed father walked out on his mother while they were living in Bennett Street, Bondi. In 1936, George found a job as a paper-pattern cutter for the Australian Home Journal,spending his spare time dancing and taking photographs.
One of his finest tableau pictures, taken on October 8, 1939 just after the outbreak of World War II, shows no less than eight members of the gym, with the white-capped Alf Stanbrough in the key position of bearer. At the apex is Charlie Lusty - the only member of the group still alive. Within two years, beachobatics had disappeared from Bondi. One by one, the men went off to war - except for Lusty, who was in a protected profession.
Caddy himself was stationed near Brisbane as a gunner in an anti-aircraft battery. When he returned to civilian life in 1946, he seems to have abandoned dancing and photography. The reasons aren't entirely clear, though he married Betty York in 1943, becoming a father when Paul was born the following year. "Home duties probably won out," Davies says.
As well, beachobatics - influenced by the health and fitness philosophies of pre-Nazi Germany - had been born in a more carefree age. Of the seven men in the tableau picture who went to war, "two never came back", Davies says. "Others came back completely shattered."
As for George Caddy, he packed away his cameras, stored his negatives in a cardboard box and put his days as "The Bondi Jitterbug" behind him.
Fortunately, his photographs have survived.