[Milsurplus] WRR-2 Variants?

[Robert Goff]

I'm looking for information on the differences between the WRR-2, 2A and 2B.

I see that manuals covering the latter two versions are available from
several sources in both electronic and paper format. I believe one is
Navships 94715.

I have a WRR-2 (plain) which I would like to get going, so I'm
naturally curious about the differences between the different
contracts.

Anybody know?
Thanks,
Robert
W7MKA