noun
platinum wedding anniversary; 70th (or 75th) wedding anniversary
Refers to the celebration of a 70th or sometimes 75th wedding anniversary. The exact year can vary by tradition.
祖父母は今年プラチナ婚式を迎えます。
My grandparents will celebrate their platinum wedding anniversary this year.
Compound of プラチナ (platinum) and 婚式 (wedding ceremony/anniversary), modeled after terms like 金婚式 (golden wedding). The exact anniversary year (70th or 75th) is not universally fixed.