I've fired a few different derringers....at least one FIE and some American Derringers, etc.....and the whole lot of them were pretty terrible little guns.
The one's I've fired were in .38 spl, . 45 Colt, .410 shotshell....and they all had trigger pulls that were so far above 10 lbs it was ridiculous.
They're meant as "belly guns" for close in work....and yes, I think Novely about describes what they are......every used gun shop, pawn shop I've ever been in has at least a dozen of them for sale...( and they don't sell many )...
at least dry fire it before you buy, see if you can live with the trigger that is in it..../ recoil is manageable for most any adult male...it isn't like you're going to put 50 rounds thru them....you'll just carry them in a pocket or whatever you want it for ...or as a novelty.
I have only one in my collection ...a 6" American Derringer...and its a "Novelty"...at best ! Its a model 6 ....if you want to look at their website...their website is a lot more cool than their guns....( I inherited this one / I didn't buy it ) !!!
http://www.amderringer.com/