The K2FC is distinguished by several basic differences. Among which -
The CB end-housing is attached by THREE 1/4" BSW screws
The holes in the magneto body for the HT pick-ups are smaller, and each
pick-up is held in place by a pair of screws, not by spring clips.
The cb cover is always of the screw-on ring type with brush for remote
Drive end bearing is always 18mm i.d., whereas very early standard K
series used 15mm. From some time in the 1950s, all were upped to 18mm.
It is said sometimes that Lucas put extra copper on the HT coils of K2FCs, but
we see no evidence of that from this remove, and rewinders do not treat them
differently today, as far as we know. It has also been said that no K2FC would
be allowed by Lucas to contain a coil with a break in it (due to winding mishap)
whereas standard ones would be allowed a soldered repair if necessary. Folklore
or fact, who knows now?