KX4S AND W4DR
Directly from March 1993 CQ Magazine it says:
Yes, folks, all that radio equipment and all those antennas are intended to produce that little piece of cardboard! That's Bill Bunting, KX4S, at the operating desk as chief op Bob Eshleman, W4DR, proudly shows off his QSL from the Myanmar DXpedition, XY0RR.
(Photo by Larry Mulvehill, WB2ZPI)