Michael J. Fox is wearing Casio CA-50 in Back to the Future
Casio CA-50 Calculator Watch Module 437 Back to the Future - Etsy Finland
Vintage Casio Ca-50 Digital Watch 1980s Back to Future Calculator WOW for sale online | eBay
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
CASIO CA-53W Calculator Watch Review - Back To 1985! - YouTube