Dobro made few Model 206 guitars John Dopyera said no more than 12 or 15 as showpieces for trade shows or by special order.

For months the inventor of the resonator guitar spent his evenings and weekends working with his brother, Rudy, on a secret project a single-cone guitar they believed superior to the National Triolian.

John Dopyera developed the biscuit-bridge system for use in a ukulele, but felt the design did not sustain well enough when enlarged for a guitar.

Nationals president, George Beauchamp, overruled Dopyera and rushed the Triolian into production in late 1928.

Beauchamp and Dopyera had been rubbing each other the wrong way for some time, and this came as the last straw.

A radiating spider carried the sound from the bridge to the edges of the cone.

Without a block of wood choking it, the inverted resonator vibrated freely and sustained notes longer than the biscuit-bridge cone.

Rudy and Emil (later called Ed) Dopyera left National soon after John.

Emil, the salesman, showed the prototype guitar to dealers in southern California and took the first orders.

Two other brothers, Louis and Bob, helped finance the venture.

In the spring of 29 Dobro started production in the back room of Russell Plating Company.

Because prices changed from year to year, guitars changed model numbers, and the same model number may have applied to several different guitars.

For instance, 1929s Model 45 was a dark, unbound student guitar, 1932s Model 45 was a bound single-screenhole Cyclops, and by late 33 the Model 45 was a spruce-top with two screenholes.

These were Dobro guitars that in those particular years carried a list price of 45.

It was not a good system, and the company stuck it with until production ceased at the dawn of World War II.

By 31 Dobro introduced the Model 50 tenor guitar, with a bound fretboard and a mandolin-size resonator in a guitar-size body.

Later in the 30s Regal in Chicago confused things by numbering a run of Dobros across the same range.

By 1933 Dobro moved the screws to the half-hour points so a repairman could open a guitar without removing the tailpiece.

The unbound student guitar, its hardware painted silver instead of plated, dropped in price to become the Model 36.

The Model 55 became the Model 56 (some ads specified hardware plated with nickel instead of chrome).

The scrollwork Model 60 evolved into two styles: the Model 66, with a fretboard of red bean wood, and the Model 66-B, with a bound body.

The Model 85 became the Model 86, with engraving added on the coverplate.

The Model 156 was walnut with an inlaid fretboard and gold plating.

Dobros tenor guitar came in three models, the 50, 75, and 100, with details corresponding to the Models 56, 76, and 106.

Gibson Dobro Serial Numbers