This nice HO gauge locomotive by Roco is 63840 a SBB Re 4/4 electric locomotive in green livery. It has running number 11128.

The Re 420, originally (and still widely called) Re 4/4 II, series are the most common electric locomotives of the Swiss Federal Railways. They are used for passenger services throughout Switzerland alone or in pairs. For freight services, they are sometimes paired with the Re 620, especially in mountainous regions. That pairing is referred to by the term Re 10/10. 

The Re 420 locomotives were produced over a period of 21 years, from 1964 to 1985.

The loco is in good condition as you can see in the pictures, it is fully tested and runs well with working lights. 

It comes complete with its box. The box is in good if slightly shelf worn condition. 

Overall this is a really nice scale locomotive and would look fantastic on a layout.

Do please have a look at my other listings, I typically have various HO and OO locos on offer as well as an extensive range of imported N gauge locos and other items. 

Note: I do recommend all locos are cleaned & serviced, as they have some age to them even if the quality looks at the highest level (fairly standard advice for all locos!).