CH 1957 FDC DX 1-6 CH Symbolic representations and Universal Postal Monument ill no address

Switzerland 1957 DX (Official Stamps - Universal Postal Union - UPU - Union postale universelle, Berne)
Symbolic representations and Universal Postal Monument, 6 values, SBK DX 1-6, Michel 1-6,
FDC illustrated without address, Top Quality