[edit] Bigsby
Epiphone Casino VT with Bigsby.Main article: Bigsby
The first commercially successful tremolo arm was the Bigsby vibrato tailpiece, most often just called a Bigsby, and invented by Paul Bigsby. The exact date of its first availability is uncertain, as Bigsby kept few records, but it was on Bigsby-built guitars photographed in 1952, in what became its standard form. The design uses a spring-loaded arm that rotates a cylindrical bar in the tailpiece, varying the string tension to create vibrato and other pitch variations. The string tension is balanced against a single, short hellical compression spring, positioned under the arm pivot.
To this day, the Bigsby enjoys some popularity, especially on hollow body guitars, and is available as a factory-fitted option on top-line models both hollow and solid bodied from many makers, and as an aftermarket addition (requiring some skill to fit however). It remains the only widely used design whose mechanism is entirely above the belly of the guitar body, making it the only design particularly suitable for acoustic and semi-acoustic guitars.
I had pictures on my old hard drive of a 12 string with a floyd someone fabbed up..