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 usually is large for its time, the minimum size being 35x42x10mm with a maximum of 38mm (in the conventional shapes at least), it has a 21600 beat rate, and all kinds of complications or lack thereof. There is time only, date, daydate, a weekdater variant, hand winding and the ability to precisely set the seconds though a hacking lever. The weekdater window of course was used for the daydate version, but that was not all, in some models even the King Seiko caliber 5626 was put inside and the watch designated Lord-Matic De Luxe, elevating the beat rate from 21600 to 28800.
The 56 caliber seems to have been developed between two others, the 51 (starting in 1967), and the 52 (starting in 1970), the latter also being used for the Lord-Matic Special 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 flatten its mid to high grade movements, many novel design elements were incorporated into the 56LM apart 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 Seikos, it was not chosen for the task of resurrecting the mechanical watch after Seiko's world wide quartz onslaught. The decision was made to use the 52 caliber, rebranded as the 4s15 in all of its high end Laurel, Alpinists and SUS siblings. Even the Grand Seiko eventually used it as caliber 4S when its quartz only days were numbered.
I really think Seiko was approaching the epitome of automatic movement design in these 52 asnd 56 calibers, leading up to most modern calibers used today.