The Targum names them precisely: thy seal, and thy mantle, and thy staff which is in thy hand (Genesis 38:18). Tamar did not ask for silver. She asked for the three objects a man of standing would not give up unless he meant to return.
The Sages of Bereshit Rabbah dwelled on these three items. The seal (chotam) marked Judah's name on documents — his legal self. The mantle (petilin, the cord) fastened his outer robe — his public garment. The staff was his walking rod, his authority on the road. Together they amount to a small portable portrait of a tribal leader. The Targum Pseudo-Jonathan, redacted in the Land of Israel in the early centuries of the common era, lists the three items in exactly the form that would later let the court scene work: unmistakable, identifiable tokens.
What Tamar is doing, in the tradition's reading, is archival. She is collecting evidence. She knows that if she is later accused, she will need more than her word. She will need the objects themselves, held in her hand, to force a powerful man to recognize his own handwriting.
And there is a quieter theological note. The Targum says Judah gave them to her. A man's public identity is not taken from him; he hands it over. The seal, the mantle, the staff walk away with a veiled stranger because, for a few hours, he has stopped being the Judah who guards them.
The midrashic lesson is simple and hard. The signs of who we are in the world — our name, our robe, our staff — can be lost in a moment of private indifference. They can also, if we are fortunate, be given back to us as witnesses that call us back to ourselves.