this is the first promaster to use an eco drive movement, the 7878. It
was known as the solar tech, eco drive came later.
it would appear to be quite a rare watch as i cant find another with "solar tech" on the dial and i would imagine being so early they were only released in japan
its a "front loader" and although it looks small it measures 43mm including the crown with 20mm lug width, the visible part of the dial is small though at only 12.5 mm and this probably gives the impression of a small watch overall.
fortunately its in good condition as parts for these IE crystal, bezel, hands etc are not available anywhere, but its does take a standard eco drive Li-on rechargeable cell