Australia: Pillar Box V. Country Box?

Two rather ordinary cancels from different parts of Australia (1938). I'm curious, though: What's the difference between a "Pillar Box" and a "Country Box"?

Great question,
it looks obvious, but for me
defies definition.
I look forward to replies.
(BTW I believe the country box is type S22)

I believe they mean a country box is a free standing rural mail box that has regular pick ups that anyone can deposit mail into.
While the pillar box is an urban free standing box functioning in the same way as the country box.

That's what common sense would dictate,
but I do not recall ever seeing one.
Albeit, I am not in touch with country Queensland
postal practice.

More information about these cancellations could be found in J. C. Smith's "The Postal Cancels of Brisbane, Sydney and Perth" [1991]?
A review of this publication mentions the following:
"For those unfamiliar with these dies, they are primarily square and bear wording such as POSTED CITY BOX, POSTED PILLAR BOX, POSTED IN PILLARS, POSTED IN COUNTRY BOX, POSTED OVERSEAS BOX, POSTED IN CIRCULAR BOX, POSTED INTERSTATE BOX, POSTED AIRMAIL BOX and POSTED IN SUBURBAN BOX."

http://www.stampprinters.info/plb19.pdf

Great Stuff 22crows,
all new strikes for me.
Thanks for posting.

I knew the search function would work on this one :) So are these pretty common ?
While trying to find more cinderellas for a different thread I came across this in the postcard box.

One we use in Country Western Australia
is RMB = Roadside mail Box.

I have for quite some time been procrastinating on taking my
camera on my bicycle rides, I am up around 70Kms now,
and often pass some great RMB's, Ned Kelly and the like.
I must get around to doing that.
Usually I am too busy sucking in oxygen, than even
thinking about stopping for a snapshot.

RMB is a personal mail box just like the one you have to receive your post but in the country they are far from the home usually and are on a road so the postie can drive along and deliver without going to the house. It is not a public mail box.