W7BRS QSL from 1940s

I have just four QSL cards from operators who worked my grandfather W7BRS in the 1940s. I'm positive that my grand-father was active in sending QSL, but I have no way to verify to be honest. My older relatives in the family had once access to his papers but I have no access to them now. For all I know, this is it.

Thankfully, I do have the originals on paper stored safely.

The callsigns of those ops are W7HDC, W7ALH, W7AFZ, and W7BPW They are below:

The remarkable thing about the last "QSL" card is the use of "CW" abbreviations in the actual card. Not just once or twice, but throughout the hand-written note. Remarkable. I'd like to know more about the habit/patterns of early QSL cards. Drop me a line if you have insight/references to follow up?