The apostrophe also indicates missing letters i.e. Amos 'n' Andy (Amos and
Andy), 'Tis (it is), F'rinstance (for instance).
KC's could be kilocyc'les although more proper would probably be k'c's
although stupid.

Quig

"Roger D Johnson" wrote in message
...
3599 kc's? The apostrophe indicates possession. Is that
intended to be plural? Kilocycles is already plural.
Rather like the lids that use 73s.