The Seiko Lord-Matic, Suwa division, is a self-winding 23 jewels watch. It features a clean dial with or without the applied LM logo - which was added from 1970 onward to the line-up. Inside is in fact the King Seiko 56 base movement, a high end automatic that was thinner then all other auto’s of the time.
The Lord-Matic made by the Suwa division is large for its time, the minimum size being 35x42x10mm, it has a 21600 beat rate, and all kinds of complications or lack thereof. Time only, hand winding and the ability to precisely set the seconds though a hacking lever. In some cases a weekdater window was used for the daydate version and even the King Seiko caliber 5626 was put inside for the De Luxe Lord-Matic, elevating the beat rate from 21600 to 28800.
The 56 stream seems to have been developed between two other caliber streams, the 51 (starting in 1967), and the 52 (starting in 1970), actually used for the Lord_Matic Special caliber 5216.
When the 51 was developed, it had a thickness of 4.9mm. The 56 had a reduced thickness of 4.3mm, and the 52 further reduced the movements thickness to 3.9mm.
In this continuing effort to reduce the thickness of its mid to high grade movements, many novel design elements were incorporated into the 56LM part from the mentioned complications. At the beginning of their roughly ten year production run (1968-1977) the Lord-Matics were a one piece design in that you could only remove the movement from the front, thereby increasing the water-proofing. For maintenance of the watch, it is opened through and by removing the acrylic glass.
Although the 56 series was later upgraded and even used in chronometer grade King Seiko's, sadly that it was not chosen for the task when Seiko made the decision to resurrect the 52 series as the 4s15, with all of its siblings. I really think Seiko was approaching the epitome of automatic movement design in this caliber, and the 4s series is a compromise of some excellent ideas.