Casio CA-50 Calculator Watch Module 437 Back to the Future - Etsy 日本
CASIO SILVER TONE,BLACK RESIN,DIGITAL CHRONO,CALCULATOR,ALARM WATCH CA -56-1CFのeBay公認海外通販|セカイモン
Marty Mcfly Casio CA-50, Common to popular belief the CA-50 was the original Casio worn by Marty Mcfly, before he wore the CA-53 in the later scenes! This is mine I sourced