There are a large number of records relating to gifts for the 1954 tour in the National Archives of Australia.
Unfortunately, none of them has been digitised and so are not available online. More importantly, not all of the files have been examined and so they are not yet classified as open.
Re the jeweller Paul Schneller. I keep hitting a glitch in searching for persons by that name in the immigration records. The only person I can find is a French national who arrived in Melbourne in 1950 and left the country in 1961. As this immigration file has not been digitised, I cannot see his occupation.
The file I found yesterday for Joseph Mann said he was a clock maker.
I am hoping that the Royal Collection and the Powerhouse curators will release more information.