The sealed sources containing a mixture of 10±5% µCi (370±5% KBq) 137Cs, 20±5% µCi (740 KBq) 60Co, and 20±5% µCi (740±5% KBq) 152Eu based on inorganic exchangers, preparations were made, standards were met, and quality checks were passed satisfactorily. ZrSiW matrix retaining 137Cs, 60Co, and 152Eu, the core of the sealed source for the appropriate radioisotope was cleaned and dried before use. A circular disc-shaped acrylic canister was filled with a calibrated quantity of the matrix. Prior to being sealed, the source underwent quality control inspections, followed by radiometric standardization and encapsulation, before being placed on the local market to calibrate radiation detection and measurement equipment. Standard radionuclide sources generating multi-gamma rays over a broad energy range, such as 152Eu and 154Eu sources, are chosen for determining multiple efficiency values (at various energies) per measurement. The lack of accurate coincident summation and the merging of neighboring gamma energy peaks, which can happen with multi-photon sources, makes ordinary single-photon radionuclide sources, such 51Cr and 137Cs sources, beneficial for high-accuracy.