Standard refrigerator car type Ibopqs (length 134mm) is used as the basis car for the Märklin Catalog Cars Series (note: Märklin beer cars series also uses this type Ibopqs car)

Catalog YEAR	ART.NO.	SIDE MOTIVE	UNIQUE FEATURE
1929*	45900		From the Manufacturer of Very Fine Metal Toys 1929 Baureihe (Class) 39 steam locomotive (the legendary Prussian P10)  next to an abstractly depicted older design electric locomotive in front of a large station shed
1930*	45901		Through the History of Märklin Catalog Title Pages 1930 Baureihe (Class) 01 before the background of a massive mountain as the locomotive enters a tunnel with an express train
1931*	45902		Through the History of Märklin Catalog Title Pages 1931 Baureihe (Class 95) steam locomotive (former Prussian T20) with a mixed freight train. In background a BBÖ (Austrian Federal Railway) class 214. The painting adorning this car shows a scene at a large station with four trains spanned by a signal bridge as well as a gantry-style signal tower.
1932*	45903		Through the History of Märklin Catalog Title Pages 1932 The painting adorning this car shows Austria‘s largest steam locomotive, the class 12 of the BBÖ. The prototype was built from 1928 to 1936, and at this time it was brand new and was still being built. However, this locomotive was never done by Märklin as a model.
1933*	45904		Through the History of Märklin Catalog Title Pages 1933 The legendary, fabled class Ce 6/8 II SBB “Crocodile” as a miniature in ne sheet metal. The only difference between reality and artistic realization: The “Croc” from Märklin at this time only came in a green paint scheme. In addition to the Crocodile, the “Flying Hamburger” was running and at that time was the “Racer” in the Märklin assortment.
1934*	45906		Through the History of Märklin Catalog Title Pages 1934 The painting adorning this car shows the scenery at a snowy country station in the foothills of the Alps with a mighty mountain in the background early in the afternoon around 2.
1935*	45905		Through the History of Märklin Catalog Title Pages 1935 The painting adorning this car shows a larger passenger station with a massive approach track complex, including the station hall that can be recognized at the upper edge of the image. On the rearmost track stands a class 95 locomotive (former Prussian T20) with a passenger train. The neighboring track hosts probably the largest – and for many model train operators unattainable – highlight from Märklin in the Thirties: The Crocodile!
1936*	45907		Through the History of Märklin Catalog Title Pages 1936 The train on the painting is unmistakably the Henschel-Wegmann Train, pulled by the locomotive legend 61 002, which lives on today in several (large) parts in the at least equally legendary express locomotive 18 201. The paint scheme of the locomotive and car consist is coincidentally the same as the 1928 Rheingold car consist. At the time of the origin of this painting and the catalog on which the painting was the cover theme, the trains was brand spanking new on the German State Railroad Company (DRG).
1937*	45908*		Through the History of Märklin Catalog Title Pages 1937 The painting that decorates this car shows a beautiful winter motif at a tunnel entrance or exit on an electrified two-track main line. A green class E04 loco hauling an express train of the same color is exiting the tunnel just as another express train has disappeared into the tunnel, and the viewer can just make out the end-of-train discs at the top of the last car.

(*) denotes catalog car owned by me

Interested to know how the past Märklin annual catalogs look like, check here (Source: Jan Frobenius)