Requirements to be an 'exchanger'

This is a post about racism.
We came into a nice little inventory haul the other day, mostly postcards and photographs, but it also included other paper items, lovingly known as ephemera.  Ephemera is typically a paper item that has a specific use and is usually discarded.  A ticket to a sporting event is a good example.
One of these pieces of ephemera was a combination advertisement and application to join a club which exchanged items.  You could even chose the items you wanted to exchange - postcards, coins, stamps and several other things.  It would be a fun way to advance a hobby.   The address for the organization was Nashville, Tennessee, and it looked to be 1940's - 1950's, and someone had filled it out.
There were only two requirements you had to meet before you joined - you had to be serious, and you had to be white.  Actually, being white was listed first.
My first thought was how could they verify either requirement?
My second thought was that the world has changed a bit since then.
And my third thought wandered to my home town, Hindman, Kentucky.
Hindman, Kentucky is the county seat of Knott County.  It is by far the largest town in the county, but it's population has never, at anytime in recorded history (or pre-history for that matter) broke the 1,000 barrier.  It is a tiny place, and it is where I spent the first years of my life.   My parents were both school teachers, but I guess it wasn't working out financially or security wise, so my father (who was in the reserves) went to active duty in the Air Force, and for the next 10 years I found myself living in various places in the USA and Europe.   Although we'd go back for visits, there was a disconnect with me and Hindman.   I lost contact with it.
I went to college in Kentucky - it was the only place I considered home at the time.  As an 18 year old freshman, I met a classmate who was black, who told me he was from Knott County.  I didn't say anything, but I remember being confused because I didnt realize any black people lived in Knott County.   I was born there, grew up there, found myself back there frequently, and in all my life I had never seen a black person in Knott County.  
So, my curiosity aroused, I looked around and came to my own conclusions.
First - there were black people living in Knott County.  I don't know how many.
Second - it was obvious that the social arrangements that existed between the black and white citizens of Knott County were solidified long before I was born.  There was no need for any "whites only" signs or any other outward manifestations of Jim Crow laws in Hindman, because black people did not go there.   As a county seat, Hindman was the location of many local government services.  Property deeds, car registrations, things like that.  I often wondered, if black people never went to Hindman, how did they receive those services.  I still don't know. Perhaps they didn't receive those services.
Third - I realized I had lived my whole life up to that point with a very false perception.
So, the society I grew up in was not quite as benign as I thought it was...a society that was so thoroughly segregated, I didn't even realize it.  If you wanted someone to join some organization in Hindman, Kentucky in the 1950s, for example, there would be no need to include being "white" as a requirement.  I'm sure it was understood - by everybody.
I can't remember that classmate's name, and he has no idea how much of a shock and a revelation he was to me.  Because of him I noticed things I never noticed before.
But I didn't go around trying to change society.  I, who had spent my formative years bouncing around the USA and Europe, joined the Army after college and continued to bounce around the USA and Europe.
This little piece of ephemera brought back some thoughts.