Beyond 50 years of marriage each anniversary year does not have a symbol or material rather every 5 years is celebrated with the exception of 65 years of marriage which has no symbol associated with the year.
Although there is a symbol for every 5th year up until 100 years of marriage we have yet to see anyone achieve an anniversary over 90 years although given people are now living longer we feel this is only a matter of time before this occurs. Wikipedia maintain a list of couples who have had the longest marriage together.