You do not come across these very often !  An  Antony Mount designed  model with castings supplied by Polly Model Engineeringof this is an   Easton & Anderson Grasshopper  beam engine. Extremley well built the  Engine itself is  aprox 71/2 inches long (19cm) x 5 inches wide (13cm) x 6 3/4 (17cm) high.Flywheel is 5 1/4 (13.5 cm)  Mounted on a wood base aprox 91/4 long x 6 3/4 wide .This in turn has  4 rubber feet. Runs well on air.