Write a note of endearment with a silver pen. Engrave the pen, and package the stationery and pen together with a ribbon.
Wrap up any simple gift in beautiful silver gift wrap.
Have a secret message engraved on the inside of a silver ring or another piece of jewelry or cuff links.
For another couple
Give them a silver piggy bank with a cash surprise inside.
25 years is a long time. Be sure to tell your special someone just how much these years have meant to you with the perfect card.