The anniversary gift list has been cobbled together over the centuries, but it was first codified by the queen of etiquette, Emily Post, who published a list of eight milestone anniversaries with appropriate gifts in 1922. The traditional list, as we now know it, was put out in 1937 by the American National Retail jeweler Association. Later a modern list appeared that offered alternatives to the traditional lists and filled in years that weren't covered previously.
Ultimately, the list is just a guide. In 1965, Elinor Ames wrote in Etiquette for Moderns: 'Although the first anniversary is considered the paper or plastic one, the second, cotton, and so on, it is not mandatory that the gift be of the "appropriate" material or composition for the specific year.'
'The exception is in the case of the 10th (tin or aluminum) and 25th, which is known as the "silver anniversary." For other years it is equally correct and often more interesting, to buy what seems appropriate for the particular couple and carry out the theme in the wrapping or decorating of the package. Thus a gift for the seventh anniversary could be wrapped in copper-colored paper, a lace handkerchief might decorate the package for the 13th, and so on.'
Tenth: tin/ aluminum
Thirty-fifth: coral/ jade
75 years: Diamonds. Although Queen Victoria, possibly realizing she might not reign for 75 years, celebrated her 60th year on the throne in 1897 with diamonds. So now the gems are appropriate for both.