The M4 Alaskan Survival Derringer        Made by American Derringer, this little two shot pistol is marketed as a survival gun able to take down large game and small game simultaneously. The top barrel is chambered for the large .45-70 cartridge, while the bottom barrel is chambered for .410 shotshell/.45 long colt.  The derringer is single action only but has a safety which disengages when the hammer is cocked.  They cost around $600-$700 new.