Got this B640 off ebay but it seems to be made out of solid steel. I found a post on watchcrunch of an identical looking B640 saying its fake because when cycling
Casio B640WB-1BEF Review - The Digital Watch Batman Would Love — Ben's Watch Club
Casio B640WB-1BEF Review - The Digital Watch Batman Would Love — Ben's Watch Club
Casio | Accessories | Casio Digital Silver Stainless Steel Band Watch | Poshmark
Casio Illuminator Rose Gold Men's Watch - B640WC-5A | eBay
Casio B640WB-1BEF Review - The Digital Watch Batman Would Love — Ben's Watch Club