Issued in 1978, this 4 kopek commemorative celebrates the construction of the “Soyuz” natural gas pipeline, symbolizing energy cooperation and solidarity among socialist nations. The stylized white flame rising from a pipeline forms the central motif, while the flags of allied states emphasize international partnership. Its clean blue background and bold graphic design reflect classic late-Soviet industrial propaganda art. A strong thematic piece for collectors of energy, industry, and Cold War geopolitics. Popular within topical collections on pipelines, engineering, and Eastern Bloc history. Fine examples with sharp perforations and fresh color are especially desirable.