Morris Minor Owners Club

Have just discovered an ignition switch with no keys but has the following numbers on the 'drum' 31973K 11 68.
Presumably the switch was made in Nov '68 but is the key no in the first set of numbers?

Thanks all

It's sometimes on the barrel - but would be looking for FS or FP 123. The number is usually 3 character. If it's well used - just about any key (or even a screwdriver) will turn it!