Dave,

like most classics, their originals were built in wood as is the case with the Elation version Steve built and offers. It's possible that when the mold was made for your model, they didn't include the vertical. This was not uncommon with early glass fuses. It was only in the late 70's, early 80's that glass fuses started to have integral fins. As an example, glass Dirty Birdy fuses had no glass fin while the follow up UFO did.

Mind you, with a fuse design like yours, an integral follow fuse fin (as in Steve's Pacemaker build) must be made a part of the fuse unless a lot of work is done to blend a thicker foiled vertical into the glass. It could be that your model is a different design as well.

David