This really nice 3-rail AC HO gauge loco by Marklin is 3319 an ÖBB BR 50 steam locomotive in black livery , it has running number 50 1805. 

The DRB Class 50 is a German class of 2-10-0 locomotive, built from 1939 as a standard locomotive for hauling goods trains. This class was procured as part of the German preparations for war that led into the Second World War. Up to 1948, 3,164 Class 50 engines were built by almost all the European locomotive factories. At the end of the steam locomotive era, they became virtually a universal class of mixed-traffic steam engine that, thanks to their low axle load, could even be employed on branch lines with light track beds. The Deutsche Bundesbahn grouped the locomotives into Classes 050, 051, 052 and 053 from 1968 so that the numbers were computer-compatible.

Some of the class were used by the Polish State Railways as type Ty5. The last DB locomotives were retired from Duisburg-Wedau in 1977.

Only 350 examples of Class 50 engines remained in with the DR in East Germany after the war. Because only a small number of the numerous Class 44 fleet went to East Germany, the DRB Class 52 was the predominant goods train locomotive in many areas there. Of the Class 50s, 208 units were rebuilt into Class 50.35-37 engines. The original locomotives ran mainly in the south. From the middle of the 1970s they were retired in large numbers, so that in the 1980s they were real rarities. Nevertheless, the last ones ended their active duties in 1987 together with the rebuilds (Rekoloks).

The loco is in good condition as you can see in the pictures, We are unable to test it as we do not have a three rail AC test rig or track, so we have not tested it but can see no reason why it would not run. It is sold in untested condition, this means that it may not run, and as such it is not being sold in running condition. However a complete external visual inspection has shown no reason why this loco would not run and the overall condition is very good. 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!).