Hello Irene,
Was it a German research company?
Like many surnames, Winkler is derived from an occupation. Winkel is the German word for an angle, but also for a recess or nook. In Low German (spoken in northern and north-eastern Germany) and Dutch, the word was used to describe a small general shop. The Winkler was the shopkeeper. It was also a term for handyman.
As such, it was not specific to a particular region or German-speaking state.
Which census records are you referring to?
Justin