Yes, it's a Miyata serial number and they were a known contract manufacturer for Univega during this period. The serial number indicates 1983 manufacture but it's so high that it's almost certainly a 1984 model. Consequently, you can use the extant 1984 catalogue on the Univega Catalog Project website as your reference.

The frames were designed by Ben Lawee's company and they don't directly correlate to any Miyata model. I think most people say the Pro Miyata because a couple of years later, in 1986, Miyata incorporated similar fast back seat stays into that model.

Regardless, it's a high grade frame with tubing and geometry that is comparable to Miyata's Professional Racing Series models of the era. Of course, the workmanship is also excellent, with Miyata being arguably the best of the Japanese mass volume manufacturers. As further evidence of their dedication to quality, Miyata was the only Japanese manufacturer who supplied European pro teams in the early 1980s and only bicycle to manufacturer to draw their own butted CrMo tubing.