Much as I would love to use this to build my dream 16800, nothing says "legitimately procured Rolex midcase" like the first digits of the serial number being scratched off while the rest of the case is in excellent condition...
https://www.ebay.co.uk/itm/No-reserve-Rolex-16800-case-with-7mm-Crown-703-AND-tube/132917616569
https://www.ebay.co.uk/itm/No-reserve-Rolex-16800-case-with-7mm-Crown-703-AND-tube/132917616569