Seiko 5717-8990 Single button chronograph from 1964

A lovely vintage Seiko 5717 single button chronograph from 1964. Fully working; keeps good time and resets correctly. The sunburst dial is in nice condition, with just a couple of small spots visible to the left of centre and one over the 'Chronograph' wording. The crystal is in reasonable condition with just a few marks/scratches. The bezel rotates smoothly. The case back has worn so the serial number is visible though the logo and model have faded.  A lovely watch that is an important model in the evolution of the Seiko wristwatch