Westfalia-Werke is the German company responsible for by far the most popular Camper conversions of VW T2′s in the US. The company offered ‘officially recognised by Volkswagen’ conversions from the first VW Buses all the way through to 1999, when Daimler Chrysler (Mercedes Benz) bought 49% of the company, and in 2001 bought the remaining share, ending the relationship with VW.
The first Westfalia conversions of the T2 came shortly after the introduction of the first Buses in 1951, and had redesigned interiors from the standard buses seating, but did not have the pop top, so you struggled to stand up inside the van. a cutaway diagram below shows the interior structure:
Later Westfalias had the pop top which differentiated from Dormobile conversions by lifting in a small box-section fashion, or using a front or rear hinge, rather than side hinged like a dormobile: