Another Wayback Machine Double-Action

The odd duck pictured above is one of the several models of revolver made under the patent filed by C. S. Pettengill on July 22, 1856.
See entire patent here.
I posted a picture of it earlier here.
At the time I'd assumed that it was just one of the many transitional revolvers which were nothing more than evolved pepperboxes.
Due to their affordabilty compared with other pistols produced in the UK, the transitionals were popular in Britain long after they went out of favor here .
Example below:

The transitional revolvers were nothing more than pepperboxes with a single barrel. Lighter (A significant consideration with a full-sized pistol of say .44 caliber), faster to clean but losing some punch due to the cylinder gap.
But the Pettengill - that was a whole different breed of cat.

First off, it's double-action. Not a biggie, so's the transitional pictured above.
But it's got a hidden hammer - and a solid frame.
The solid frame was still innovative for 1856 being two years ahead of the Remington 1858 New Model Army. Still, it was patented a year after Colt's first solid frame revolver the 1855 Pocket was put into production.
The solid frame itself goes back a few years before to the British designed Adams revolver.

1851 is the date for this modern-looking handgun, the first successful double-action and the first with a solid frame.
And they weren't kidding when they said "solid frame". Unlike the Colt Pocket and the Remington New Model it had no screw-on barrel. The entire thing was milled from one chunk of steel, barrel, frame and butt.
Having been made in the European tradition, everything was hand-fitted and therefore they were expensive and parts interchangeability was virtually non-existent.
But, back to the Pettengill.
Pettengill's scheme was that the trigger and hammer were mounted on the same pivot while the main spring wasn't anchored to the frame anywhere but was attached to the hammer and the "tumbler".
What's more, the hammer in it's normal, at-rest position, was raised. When the trigger was pulled the "tumbler" (Pettengill's word for what the schematics for the Colts refer to as the "hand") advanced the cylinder while simultaneously tensioning the main spring. The sear, which is a separate piece unattached to the trigger releases when all the ducks are in a row and boom. As trigger relaxes pulling the tumbler down a separate spring pushes the hammer back to where it belongs.

As you can see from the photo the design evolved somewhat between the patent date and actual production in 1862.
More to the point, several other folks poked their oar in (Two subsequent, additional patents) with the unsurprising end result being a committee-designed door stop.
Although the serial numbers go up to 3000, only 2001 were delivered to the military for $20 each (I checked with the inflation calculator folks. $20 in 1862 equals around $425 in 2009 dollars. Not a bad price but not what the government should be paying.
They were expensive to produce and rather finicky.
Having been manufactured by Rogers and Spencer of Utica, N.Y. the design was sent back to the drawing board.
The folks at R&S then took cold showers and produced the Rogers and Spencer revolver which internally functioned pretty much like the Colts and Remingtons and was single-action.
But it did retain the barrel and loading lever of the Pettengill. That's something, I guess.

The rejected Pettengill and its proud offspring - which, according to Dixie Arms, showed up too late to be ever issued to troops.
Dixie sells a repro.
A more thorough telling of the story with more pictures, here.