This Citizen Rhythm Time is not a standard production example, but a distinctive lightweight variant featuring an original resin case, produced during a short experimental period in the late 1960s. Unlike typical metal-cased Rhythm Time models, this watch employs a factory-made resin case, resulting in an exceptionally light construction that clearly sets it apart from regular civilian versions. The weight is remarkably low: Approx. 19 g without strap Approx. 24 g with leather strap fitted This extreme lightness is not incidental, but a defining characteristic of this particular variant and strongly suggests Citizen’s material experimentation during a transitional era of Japanese watchmaking. The watch is powered by the manual-winding Caliber RN2520 and fitted with a correct CTZ-signed crown, confirming originality and factory specification. The dial layout, legibility, and mechanical design closely reflect Citizen’s professional-use philosophy of the time. While the Rhythm Time line is generally understood as a civilian-oriented counterpart to the Citizen Homer—a model adopted by Japanese National Railways (JNR) for precision time management—this resin-cased example represents a further departure from standard production, prioritizing lightness and wearing comfort without sacrificing mechanical reliability. The silver-toned dial features applied hour markers and a clean, functional layout. Natural aging consistent with its age may be present and contributes positively to the authentic vintage character of the watch. With a case diameter of approximately 36.5 mm, the watch retains classic late-1960s proportions. A new leather strap is fitted for immediate wearability. This piece should be regarded as a special material-variation of the Citizen Rhythm Time, rather than a typical example, making it a compelling choice for collectors interested in uncommon case constructions and Citizen’s experimental approach during the late 1960s. Running at the time of listing. As a vintage watch, stable operation, accuracy, and water resistance are not guaranteed. The watch will be carefully packed and shipped with tracking for safe delivery. Running at the time of listing. As a vintage watch, stable operation, accuracy, and water resistance are not guaranteed. The watch will be carefully packed and shipped with tracking for safe delivery.