A morse radio (,) which hadn't been used in 40 years

[Nonverbis]

Upstream Proficiency by Virginia Evans and Jenny Dooley.

Could you tell me whether a comma is missing here?

 

[Tarheel]

If they are going to use those other commas they ought to have one there.

 

[Nonverbis]

Pardon. What other commas? If I'm not mistaken, here we can speak only about the other comma - after 'years'.
I suppose, after 'radio' the comma is necessary because it separates extra information - A Morse radio came in extra handy ...

In my opinion anything else in between should be wrapper in commas.

From your answer I can conclude that they have a choice whether to use commas or not.

 

[Tarheel]

They made a basic mistake of putting a comma between the subject and the verb.

They seem to use commas at random places.

I hope you are not using that to improve your English proficiency.

It's a rather long noun phrase, but length does not determine the necessity of commas.