[1] The official name referred to the fact that the car's engine size gave it a 4 tax horsepower (Steuer-PS) rating.

The origins of the Laubfrosch soubriquet are not entirely clear, but may refer to the fact that Opel painted all the early cars green,[2] which by tradition is a lucky colour in Germany.

Emphasis on the green colour also served to differentiate the car from the similarly shaped Citroën 5 CV which normally turned up painted yellow and was accordingly sometimes known as the Citron (lemon).

[3] The car had a four-cylinder Thermosyphon water cooled side valve engine with a claimed maximum output of 12 PS (8.8 kW) at 2,200 rpm, and a top speed of 66 km/h (41 mph).

[5] The 4/12 PS was produced through 1924 and 1925, with a few modifications in place for the second year, including a new fashionable "boat-deck" style rear end and a switch over in respect of the brakes so that in 1925 it was the footbrake pedal that operated via a cable linkage on the rear wheels and the hand brake that operated via a mechanical linkage directly on the drive shaft.

[6] In Autumn 1924, some months after the launch of the 4 / 12 PS, Opel introduced the 4 / 14 with a slightly longer wheelbase, a larger engine, and a wider range of bodies.

The three-seater "Limousine"-bodied cars were delivered in Steel Grey with a black roof while the delivery van variants were Reddish Brown".

[12] At the end of 1928 the claimed maximum power from the engine increased to 20 PS (14.7 kW) at 3,500 rpm which pushed the listed top speed up to 77 km/h (48 mph).

[13] The naming convention by which the Laubfrosch had been known as the Opel 4 PS became in one respect obsolete in 1928, since it defined the car in terms of its tax horsepower (Steuer-PS).

This was a deflationary period for the major European economies, but even in real money terms, the Laubfrosch became substantially cheaper during its production run.

It is almost certainly because of the car's success and the state of the art production facilities at Rüsselsheim that in 1929 General Motors purchased an 80% holding (subsequently increased to 100%) in the Opel family's auto business.