Thanks. That seems to have done the trick.
pri_ref.value
has
'\x1c\x01SERVERA.FOO.BAR.ORG/STAGE\x14\x01SERVERA.foo.bar.org|2188\t\x01Primary\x08\x01Active\x15\x01172.31.33.69|1972\x15\x01SERVERA.foo.bar.org|1972'

The field separator appears to be \x01. However there is smattering of 
\x1c
\x14
\t
\x08
\x15

Not sure why there are these hex characters?

Thanks to everybody's suggestions.
I fixed it this way:

I removed TEST_NODE2 as a failover member
I removed TEST_NODE1 mirror configuration
I stopped IRIS on TEST_NODE2 & TEST_NODE1
I removed all the journals as DB files IRIS.DAT are identical
I started IRIS on  TEST_NODE1 then  TEST_NODE2 
I configured the mirror on TEST_NODE1
I configured TEST_NODE2 as a failover member
Now Mirror Monitor in SMP[System Management Portal] GUI is showing no errors

Thanks to everyone for their great feedback!!

I think I used the wrong term - by "gateway" I should have used "productions"

[In System Management Portal (SMP) , GUI menu "Interoperability"-> "Configure" -> "Production"]

By "interfaces" - In IRIS command line you can run do ^SSADMIN, which has "6. Interfacing" which when selected gives me a list of "interfaces".

What is the difference between "productions" that connect systems and "interfaces" which also appear to connect systems?