DAYTON — GEM CITY Engineering and Manufacturing (GEM), a Dayton contract manufacturer, acquired Vistek Medical, a contract manufacturer of medical components based in Ivyland, Pa., GEM said Friday, May 28.

GEM, founded in Dayton in 1936, serves customers in 18 countries from manufacturing facilities in Ohio and Thailand. The company has 120 workers in Dayton and about 110 employees in an operation near Bangkok, Thailand, said Jim Whalen, the firm’s chief executive.

With this acquisition, the firm will add about 33 employees, mostly in Pennsylvania, Whalen said. There may be some new employment in Dayton as the business grows, he said.

Vince Visco, founder of Vistek, will join the GEM executive team and continue to manage the Vistek operations, a statement from the company said.

“In our niche that we’re in, there’s no doubt” that GEM is one of the biggest contract manufacturers in Dayton, Whalen said. (A contract manufacturer doesn’t necessarily have its own product line and makes products based on customer needs.) That niche is complex electro-mechanical products, he said.

GEM’s projected 2010 revenue is more than $50 million, a 16 percent increase over 2009, Whalen said. The company attracted 13 new customers in 2009, partly through other companies leaving the manufacturing business, he said.

This acquisition is part of a growth strategy for GEM in partnership with Riverside Partners, a Boston private equity firm. Riverside is the majority owner of GEM and provided the financing for the acquisition, both firms said in an announcement.

Contact this reporter at (937) 225-2390 or tgnau@DaytonDailyNews.com.