[en] Three calibration sources were designed, developed, and fabricated for a CDV-700 ratemeter equipped with a specially-shielded 6306 G-M detector. The CDV-700/6306 has been proposed for use with the BNL Air Sampler designed for radioiodine monitoring upon a nuclear reactor accident. Specifically, three sources were constructed in a geometry identical to the BNL Air Sampler radioiodine adsorption canister, which is a silver-silica-gel filled 2.75-inch diameter right circular cylinder with a 1.0 inch daimater annulus for insertion of the 6306 G-M detector. As fabricated, each source consisted of an outer stainless steel housing, an inner ¹³³Ba impregnated polyester liner, 4 weight percent silver steel lid. Respectively, the levels of ¹³³Ba, an ¹³¹I simulant, were varied in the three sources to yield nominal CDV-700/6306 instrument responses of 200 cpm, 2000 cpm, and 20,000 cpm