The design options of the various interior plasters are abbreviated in the table on bauwion page 422 – Interior plaster as follows:
1 = Version as a single-layer interior plaster
2 = Version as a two-layer interior plaster (concealed and top plaster made of the same material)
U = Version as a concealed plaster (additional top plaster made of different material)
O = Design as top plaster (additional plaster made of different material)
Source: bauwion
