At InnoTrans 2004 ČMKS Lokomotivy exhibited its prototype Bo diesel shunter, 709.401, promoted under the brand name Effishunter. Late in 2003 the company, working together with Inekon Group, had received an order from Železnice Srbije, the State railway operator in Serbia, for ten similar machines, which ŽS planned to designate Class 621.1. The first of the batch was exhibited early in October 2005 at the International Engineering Industry trade fair in Brno, where it won a gold medal in the transport exhibits category, and the new locomotives are now being delivered.