From Wikipedia:
The Short 360 (also SD3-60; also Shorts 360)[1] is a commuter aircraft that was built by British manufacturer Short Brothers during the 1980s. The Short 360 seats up to 39 passengers and was introduced into service in November 1982. It is a larger version of the Short 330. It is also affectionately known in aviation circles as "The Shed".
The spherical depression under the model is for mounting it on a 6mm BB.