Symbols for wedding anniversary milestones.

Each anniversary year has a material attributed to it, with precious metals and gemstones forming large portions of the list. It is not so well known however there are two different list specifying what is attributed to each year, a traditional and a modern list.

Where it began.
No one is exactly sure when the tradition of giving particular gifts on specific anniversaries began, however the first recorded instance of anniversary milestone gifts came in the 16th or 17th century, in central Europe (Germanic areas). On the 25th anniversary of a wedding, the husband would give his wife a silver garland to commemorate the occasion.

Bringing it all together (the traditional list).
In 1937 The American National Jewellery Association compiled a more definitive list from various traditional gifts given across the globe. These were allotted in five year markers from the fifth anniversary through to the sixtieth, and then one more commemorating the 75th.