By default, F1 is configured to emulate the PF1 (GOLD) key. But NumLock can be used instead if you load a freeware TSR distributed with MS-Kermit, call ‘gold.com’. This was once distributed in a file called gold22.zip and came with the source code as well as a loadable binary image. (See edt-pc.el in the Emacs lisp/emulation directory for more information.)