The Seiko 6105B is a mechanical watch movement featuring a ball-bearing rotor and an excenter self-winding mechanism with just one gear stage. It is typically identified by the signature Lorsa 237B. This movement, commonly used in watches around 1960, offers several functions including automatic winding, sweep seconds, a date hand that can be set by +/-24 hours, and a calendar feature. An optional pusher at 2 o'clock can be used for adjusting the date hand.