I don't have the magazine in front of me, but I believe it was RMC September, 1971 - Moisture trap coil for compressors by Anderson, Ed
I'll be going by the train club Saturday and I can pull that issue to verify it.
<snip> I built one of the copper tube after coolers from the article you mentioned and it worked fine. I traded the unit to a friend years ago so I don't remember all of the specifics... <more snippage> I remember that piece as well, Jim, but certainly not the issue. You might give Carstens Publications a call to see if they can help track it down.</snip>