This Seiko is a Seiko Lord-Matic, Suwa division edition. It is a self-winding 23 jewels 7000 model from April 1970 - not its first production year. The early models did not have the LM logo on the dial, Seiko only started applying these on the late 1969 models and thereafter. This did not always happen consistently however, so there are in fact 4 variations of the 5606 dial text make-up.
The LM has the King Seiko 56 base movement (a high end automatic that was thinner then all other auto’s of the time). This Lord-Matic made by the Suwa division was large for its day at 36-41-09mm and has a 21600 beat rate, offers quick set day and date, hand winding and the ability to precisely set the seconds though a hacking lever.
The 56 stream seems to have been developed between two other caliber streams, the 51 (starting in 1967), and the 52 (starting in 1970). When the 51 was developed, it had a thickness of 4.9mm. The 56 had a reduced thickness of 4.3mm, and the 52 (used in the Lord-matic Special) 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 5606. At the beginning of their roughly ten year production run, during the late 1960's till 1970's, the Lordmatics (like this one) 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 used in some chronometer grade King Seiko's, I find it sad 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