In 1973 LEGO released 5 Duplo sets. The largest Duplo set from 1973 was
515-2 Building Set with a piece count of 31.
The LEGO DUPLO theme was introduced as far back as 1969 and is designed for children ages 1 to 5. It features DUPLO figures which are much larger than minifigures and DUPLO blocks which are about twice the length, width, and height of a standard System brick. Like LEGO System, DUPLO also has subthemes that are often junior versions of System themes, like Pirates and Castle and licensed themes like Disney and Super Heros.
1973 LEGO Sets
In 1973, LEGO released several new sets and themes, including the LEGO Town theme, which introduced the first minifigures with movable arms and legs. This was a major innovation for LEGO, as it allowed for much more realistic and detailed play scenarios. 1973 was also the year that LEGO introduced the LEGO DUPLO line. In addition to these new products, 1973 saw the release of several other popular LEGO sets and themes, such as the LEGO Castle theme and the LEGO Space theme. These sets, along with the new minifigures and DUPLO bricks, helped to cement LEGO's position as one of the leading toy brands in the world.