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Sawai Jai Singh himself built several metal models of the instruments which he later replicated in larger scale in masonary constructions. The Jaipur Jantar Mantar office/museum has a number of these models, most of them in metal and a few constructed in wood.
In modern times, there are a number of existing models/sundials that have been constructed around the world, inspired by the Jantar Mantar observatory instruments. One example of a model whose dial size is larger than the Laghu Samrat Yantra at Jaipur, though, of course, smaller than Jaipur's Brihat Samrat Yantra, is the Samrat Yantra constructed on the campus of the Inter University Center for Astronomy and Astrophysics (IUCAA), Pune.
Samrat Yantra in the IUCAA campus at Pune
There is a small model of a Samrat Yantra constructed inside the Kuppam campus of the Agastya Foundation