I've been curious ever since mine started developing. It was instantly obvious that they do not resemble the smooth, tri-lobed squash as shown in Amy Goldman's "Compleat Squash". If you look at the pictures on rareseeds
http://www.rareseeds.com/triamble-or-shamrock/?F_Keyword=TriambleOne photo has a deeply ribbed version and the other (which looks like it's been tampered with) is, again, smooth.
Mine are all very deeply ribbed, you might think they were a cross between the smooth Triamble version and a Queensland Blue.
If I look around the web, I'd say 90% of examples look ribbed (like mine), very few smooth.
Why are there these differences? Has the variety become crossed along the way somewhere? Is it the conditions they are grown under? Is there a particular strain that some people are using? Actually, which is the right form? They look like two different squashes to me.
Yes, I'm very curious. Does anyone know anything?