Casio CA-50 Calculator Watch Module 437 Nerd Vintage Back to - Etsy 日本
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
Vintage Casio CA-50 (437) Japan RK Back To The Future Digital Calculator Watch | eBay