Mike Andrews wrote:
There are FT-243 and FT-241 crystals; they have the same form factor,
but the FT-243 has a front plate that comes off, while the FT-241
opens from the bottom. In the FT-243, the quartz plate is not silver-
plated and soldered to the connector pins; in the FT-241, it is.

Both FT-241 and FT-243 crystals will fit in an octal socket.

Andy writes:
I remember taking the FT243 apart and washing the quartz in soap and
water when the activity got low.... Also, rubbing it with pencil
lead in order to change the frequency a little...
...... Ahhhhh........ good times.....

Andy W4OAH