I am now the proud owner of my very first Merkur train model, which is a nicely detailed tinplate tank car with the catalog number 9609.
The model comes in a colorful cardbox package. The cover text indicates that the Merkur models have been designed for Continental European hi-rail O gauge (the so called "coarse scale").
The overall impression is perfect especially when pulling 20 tank cars of the same tank car type in a row on the layout.
There are some differences compared to the catalog photos, such as the more detailed fence handrails on the one end.
Some parts are screwed together, while some other parts are punched/stamped. The detailing of the truck frames could be more embossed because the details are not sufficiently visible when the trucks are painted black.
Not everything is tinplate. As you can see the single dome with the filling cover is made of die cast metal. It would be nice to use only blackened screws (not shiny ones), but I can paint them myself, no big deal.
The tampon-printed lettering is good enough, on the black underframe better than on the white/creme tubular body, but I don't mind. 
The Castrol painting scheme is one of many product variations. In the catalog you can find more choices of further roadnames and fuel companies.
The couplers can be exchanged by unscrewing on the bottom side of the underframe. I prefer the Bing style or Darstaed style hook couplers. To attach Lenz style couplers is a challenge where you need a special adapter pieces. If I remember correctly, there should be also a 2-rail version, but if not, still it is easy to replace the wheels by insulated ones with fine scale flange profile. Practically the whole tank car can be disassembled, improved and re-assembled without any instruction manual.
I can recommend the Merkur train models to any tinplate collector to have them on the shelf or on the layout. Mid November I will visit the Merkur company at the upcoming model railroad fair IMA Köln 2016 in Cologne/Germany just to see all the good stuff with my own eyes and to chat with the company's representatives.
