The Class BCL Bay 09 were open coaches for branch line services with the Royal Bavarian State Railways (K.Bay.Sts.B.)

They included those coaches listed in the 1913 fleet register under design sheet nos.

With the growth of the Bavarian branch line network known as Lokalbahnen, there was a need for suitable coaches for local passenger services.

In the period 1909–1929, 411 wagons in classes BL, BCL, CL, DL and PPostL were procured.

[1] They all had a standard floor plan, open end-platforms with Dixi gates on the steps and gangways secured only by an iron railing.

Of the coaches built to Design Sheet 521, 18 were procured in two batches, in 1909 and 1911, from SE in Nuremberg and Rathgeber in Munich.

The platform was shortened for the wagons built to Sheets 6055.2 and 6055.3, resulting in a shorter length over buffers.

The coach body had a wooden framework covered with sheet metal on the outside and wood panels on the inside.

The remaining delivery series were equipped with main line coach steps.