This article may have been around for a while already but I just came across it on Ricahrd Binder's site: Design Features: Double Vision.

The Sheaffer Balance/Mark I Equipoise similarity that has come up a few times in this forum is there, as well as section on the Omas Paragon and Wahl Doric and a French pen called a "Globe d'Or" and the Eversharp Skyline.

It's very well presented with photo examples and fascinating if a little brief (he covers a lot of ground): certainly well worth a look and I hope you enjoy it as much as I did.

Kind regards,

Darren.