KS Casebacks

[earthphase]

I have done some digging and can't come up with firm answers....

Why and when did KS drop the gold medallion on the casebacks?

[HiBeat]

I am not an expert but it seems after moving to machine-assembled 52XX and a desire to make them 'more affordable' led to the stopping of applying medallions about 1973-ish.

[mncz]

With respect to the 56-series references, I recall reading about this in Smoo’s WUS master-post, which is a great recapitulation of KS information. He humorously remarks on the production discontinuing the gold coin, marking its end somewhere around 1972 (and, so, definitely on or before 1973). See below:

Later production runs of the 5626-7110 and the 5626-7040 chronometer, while keeping the monobloc case designs and case numbers, lost the medallion, substituting an engraved “KS” roundel instead. I pity the poor Japanese businessman, who, probably sometime in 1972, was gifted a later example 5626-7110 or 5626-7040 as a retirement present and discovered that it lacked the coveted gold medallion!

And finally, it should be noted that the 56 were all produced under Suwa. With respect to Daina Seikosha, I am under the impression that gold medallions were never employed. Early productions all featured the monobloc casing, with simple, engraved backs and later moving to screw-backs, also sporting relatively simple, utilitarian engravings.

For more detailed info, I would defer to the smoo KS history post and other resources.