Another contributor, "Jeff", has intimated that PL259's
are available in metric form.

Is this true?

If so, how does one find out which version of the SO239
is fitted to equipment?

Is the modern (say, more recent than 10 years old) Jap
gear fitted with these later plugs?

When one buys plugs and sockets from the rallies, which
ones is one getting?

Presumably there's no such thing as metric plugs in Yankland?