Content Expert Saxophones
That was a JK feature. Both my Tonekings have it, and both were made in 1957.Of course, then you had those Bundy Specials. SN 48799. You can look at the pictures on the junkdude.com website. Were these Keilwerths or German Amati's or Dörfler & Jörka or something?
What is interesting identifier is the bell roll. If you notice they don't roll the bell all the way over and instead roll it and meld it into the bottom of the bell flare. This unique feature may help identify who actually made it. I know some vintage brass (mostly Trumpets and Cornets) had this type of bell roll but I cannot recall which makes/models.
With regards to the Bundy horns you mention, they were made by JK, but were sent to D&J to get their key work put on. Then they horns were sent back to JK for final assembly. This is documented on my D&J page, and is sourced from German saxophone historian Uwe Ladwig's journal articles in Sonic: sax & brass