This is not authoritative but something I have heard more than once, during my 356 days as Technical Editor of the 356 Registry website and during my time around early 911's. So take it as a point of departure for discussion - perhaps it will jog someone's memory (Lord knows my is eroding rapidly).
My understanding is that Porsche provided shop towels with travel kits but not with tool kits. Stoddard introduced the towels in the 70's and over the years folks began to believe that Porsche had always included them in tool kits. The towels in the travel kits looked like this (Eric Chernoff photo):
Attachment 313052
Note that PORSCHE is all capital letters. There are also thin blue lines on the edges of the red borders. I had one of these in a pristine travel kit in my '60 S90 Roadster. Most of the towels produced by vendors capitalize only the first letter - Porsche - and don't have the blue lines.
Cheers,
John