Something a little out of the ordinary. L. W. Seecamp emigrated to the US from Canada after he left Germany at the end of WWII. Before founding the L. W. Seecamp Firearms Company he was an O. F. Mossberg's gun designer. His very small .25 acp, .32 acp, and .380 acp pistols are mechanical marvels.
One thing that he did was to convert Single Action 1911 pistols to Double Action/Single Action guns. Seecamp also authorized other companies to to do the conversions. My Seecamp converted Gold Cup National Match gun was done by a company, TSW, of Paramus, NJ. Here it is:
Here's what the double action mechanism looks like; what looks like a single action trigger - is. You can pull the single action trigger (although you can't do it easily, the DA Trigger blocks access) and fire the gun.