set (one's) seal to (something)

1. To put one's unique signature or official seal on something, especially a document, to indicate one's endorsement or approval. The chancellor refused to set his seal to any treaty that did not include financial aid for his country. Be sure to look over the fine print of the agreement before you set your seal to it.

2. To do or produce something in a way that demonstrates one's unique style, influence, or interpretation. Though he only produced the film, it's clear that the auteur director set his seal to it. The new CEO has made it clear she intends to set her own seal to the company. The novel is the author's attempt to set his seal to Shakespeare's "Hamlet."

set one's seal on

Also, put one's seal on. Authorize, give one's approval to, as in We can go ahead as soon as the boss sets his seal on it. This idiom alludes to the old-time practice of affixing a seal on a document as a form of verification. It also began to be used more loosely in the early 1600s.

set (or put) your seal to (or on)

mark with your own distinctive character.

The reference in both of these idioms is to the former practice of stamping your personal seal on a completed letter or other document.