This tube with a neat ripple design in the glass, found in the old appliance store I'm cleaning out, is unfortunately broken. Anyone ever seen one?

I have one in my collection,  Pitty this tube is broken
    I forgot who made this one,  but i got tubes from Magnotronics with clear rings in the tubes.  It every collector
  Wish list cause u can get see internal arc stream.

Looks like a Koloratec to me.  Not that I have one   Pity the tube is broken, it's definitely a rare bird!


Here is one example right here on the L-G, I am sure there are others posted here:
https://www.lighting-gallery.net/gallery/displayimage.php?album=search&cat=0&pos=1&pid=112837

These unique tubes were the result of efforts to improve luminous efficacy.  This particular example involves wiping thin stripes of phosphor clean to allow the internally generated light through the clear glass.  It looks much brighter on the inside the tube through the clear stripes than on the outside of the tube coated with phosphor because in addition to creating visible light through UV absorption, the phosphor absorbs some visible light on its way through the thin phosphor layer.
I am guessing there was calculations done to determine how many/width of strips to use to allow a maximum of light transfered vs light lost due to removal of some of the phosphor.

Other efficacy improvements involved grooves (GE PowerGroove) and spirals (Durotest PowerTwist) in the tube envelope to increase tube surface area.