The invention relates to a type unit (3) for a self-inking stamp (1), which comprises at least one type strip (32) that is placed over a drive wheel (33-36) which is rotatably received in two limbs (30) of a bearing part (28) and which is provided with a thumb wheel (38), and a dome-shaped cover (48) which comprises at least one slot (51) for a section of the periphery of the thumb wheel (38) of the drive wheel (33-36) to pass through, and detent elements (47) in the area of the free ends thereof. Said cover, in a position releasably fixed by engagement with the bearing part (28), covers the at least one type strip (32) in the area of the drive wheel (33-36). The two limbs (30) of the bearing part (28), on their exterior facing away from the type strip (32), are provided with two projecting detent projections (44). The cover (48), on its two faces, is provided with two projecting extensions (50) as detent elements (47) for engaging with the detent projections (44) of the bearing part (28).