487, not 467. The cheaty way to beat it is to design a dedicated chess-playing CPU with dedicated chess instructions and then you could do it in only a few bytes. I'm guessing that one of the things that allows this to be smaller than the 1K ZX Chess is that the 8086 has more sophisticated instructions, although those instructions tend to take up more bytes than Z80 instructions so you'd have to be extra careful. So if that's correct then some of the complexity has been pushed into the CPU so it's not really comparing like with like. Still an amazing achievement though.
An extension of this is, do you allow high level programming languages? Toledo NanoChess implements all modern Chess rules, and is 1255 characters of C source code. Does that count, or should you have to compile it and compare the byte size? I think it's reasonable to use the source size, so long as the language is a general purpose programming language with no dedicated chess instructions or libraries. 1K ZX Chess and BootChess are binary executable size, though, but that's ok as binary instructions are a legitimate way of programming a computer, they should not be forced to convert them into assembly language source if they don't want to.