[mattbee]

The other thing this scheme gives you is a unique image per customer, so you could use it to trace illegal copies.

When I worked on some expensive emulator software 22 years ago, floppy protection wasn't appropriate but I suggested to the boss that we use the order of linker symbols in the main executable to encode the customer's serial number.

I guess it was a No because they wanted to use a standard duplicator, but also piracy was pretty well deterred by the 486 daughter board you needed to run it :)