by a tailpiece bar to which the vibrato arm is visibly connected, similar to the Bigsby, and the mechanism is installed from the top of the instrument, similar to the floating tremolo. It combines some features of all three basic designs. The Dynamic Vibrato is often confused with the Fender floating tremolo, which it resembles. The original production runs of the two overlap by more than a decade, but the mechanisms are quite different. The existence of a few 1960s Mustangs factory fitted with the floating tremolo has probably added to the confusion. The concealed mechanism is in a chamber of a completely different shape and position, requiring an impractical amount of woodwork to convert from one to the other, and the mounting plate is of a different shape with different mounting holes. The string tension is balanced against two medium length helical springs under tension, mounted on the underside of the tremolo mounting plate, one attached to each of the two feet of the tailpiece bar. Dynamic Vibrato units may be recognized by the integrated floating bridge and the stamps "Fender" and "DYNAMIC VIBRATO". Many but not all units also have the words "PAT PEND" or "PAT. NO. 3,241,418" stamped under the word "Fender". The Dynamic Vibrato was the last of the floating bridge designs Fender discontinued, with the Mustang in 1982—and the first they reintroduced, again with the Mustang, in 1990. Other Fender designs Still another design appeared on the student model Fender Bronco, released mid-1967. This was simply known as the Fender vibrato tailpiece, or sometimes the Fender steel vibrato. It was again designed by Leo Fender although he had sold the company by the time it appeared. Basically a synchronized tremolo simplified to reduce cost, it had little popularity, and was the only Leo Fender vibrato arm design not available on any current Fender model. In 1981 G&L released the F-100 guitar with a dual-fulcrum vibrato designed by Leo Fender, one of G&L's owners. Gibson Vibrola From the 1950s, Gibson offered either a guitar-shaped or a Bigsby option. Since the early 1960s, Gibson have marketed a number of vibrato system designs under the name "Vibrola". Vibrola tailpieces include a licensed version of the Bigsby vibrato tailpiece, earlier version of (or ) using roller bridge ( filed in 1961, issued in 1964), and several in-house Gibson designs. The Gibson designs did not have the impact of the