when I was young mid teens I was a ham radio operator I had a Heathkit HW-16 CW ham rig and was quite proficient at Morse code & still can remember all the letter/numeral characters, although I have not had a ham license for over 35 years...but the jist of the story is, a ham operator would always request a QSL card which is a validation of a contact you had with somebody whether stateside or "DXing"...a QSL card is like a post card but has your own custom design and call letters on it...I am probably rambling by now, but thought about the fun of trading cards even though you had to use your own postage stamp to send one in the snail mail...I think my rarest card I had was the Liberian Embassy which as you are all probably aware of is an African nation...