This first one started life as a model DD gun (or kit) from Cobray/Leinad. The owner rounded the grip frame for an old timey look, added an under-barrel lug, built custom then color case hardened the frame.
The builder posted the pictures on the Derringer Forum, see it here
This beautiful Ruger GP100 is from Reeder Custom Guns
Pretty sure Doug Turnbull's team is responsible for this one
The 1911 pistol below comes from the folks at Standard Manufacturing, visit their website here
Another beauty from Turnbull
One of the thousands of guns on display at the National Firearms Museum. If Fairfax Virginia is too far for you to travel, fear not, they have dozens of high resolution images on their website.
The pictures above were found freely on the world wide web and are used under the guidelines of Fair Use, per Title 17 of the U.S. Code. Where possible the source has been credited. If you own the copyright to any of these images and wish them to be credited or removed, please contact me immediately.