in one recipe - I can’t remember the name but it’s in RHC and is a chocolate cake baked in a 6x 3 pan, filled with vanilla mousseline but no frosting, but mousseline is piped around the edges between the layers…..RLB mentions a “partially closed” No. 26 tip. I’ve looked all over and have found closed and open #26 tips but nothing “partial”.
Any ideas?

That cake is Miette’s Tomboy.  But I have no idea about the tip.  Anyone?

Could you close off part of the tip by bending in the pieces?  I haven’t tried this, but a suggestion—tips aren’t too expensive!

It could possibly be a petal tip used to pipe rose petals.

Hi Indysusan,
My husband recently order some hard to find tips for me at http://www.ChefTools.com . No affiliation.  Good Luck! 

i would use a LARGE tip, open star.

there are also french stars, which are open, too, but have double the number of pins.

open stars are my favorite for piping.