This very nice, and rare, 3-rail AC HO gauge locomotive by Marklin is 3095 a DB BR 75 steam loco in black livery. It has running number 74 701.  

The Prussian Class T 12 were early German passenger tank locomotives built for the Prussian state railways in large numbers. These locomotives were superheated variants of the T 11.

Although the T 12 first appeared as early as 1902 in an experimental guise, series production did not start until 1905. Besides the Prussian state railways, the engine was also procured by the Imperial Railways in Alsace-Lorraine (25 units), the Lübeck-Büchen Railway, and the Halberstadt-Blankenburg Railway.

The main sphere of operations for the T 12 was the Berlin area, where it worked the city network, ring railway, and suburban lines as a predecessor of electric S-Bahn traction. The engines had to be capable of rapid acceleration when in charge of compartment coach trains in order to achieve acceptable journey times, due to the short distances between stations on some routes. The T 12 was therefore a very powerful locomotive with strong acceleration in both running directions. In 1921 a follow-on order of 40 locomotives was built by Borsig, because the fleet was not large enough. After the electrification of much of the S-Bahn network between 1924 and 1929, the locomotives were switched to normal passenger and goods train services and shunting.

In 1950 the East German Deutsche Reichsbahn took over four of the locomotives bought by the Halberstadt-Blankenburg Railway, numbering them 74 6776–6779. The ex-Prussian Class T 12's were retired by both West and East German administrations by 1968.

A small number remain in preservation. 

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!).