Only sure-fire ways I know of if the OSIG is completely unknown:
1; JTAG/RGH to get the CPU key, dump the NAND, decrypt it, and read what it says for OSIG
2; Flash spare DVD drives of different types with stock, unspoofed firmware until one plays games (not recommended because it will pop flags)
Keep in mind that some older consoles don't have factory-defined OSIGs. For those ones, it's basically a free-for-all.
How many aledged BenQ consoles have worked with LiteOns? How many consoles have this issue come up on?