I was in my LGS about 6 months ago when a guy was buying a .410/.45LC derringer. First thing he did was snap at another customer without a mask that "he was too close", but I digress.
He was trying to open it, couldn't so the sales guy showed him, to which he replied "can you write that down for me?"
He then asked if he could shoot .38 spl with it.
Told "no", he moved on to ask if he could get a shoulder holster for it.
I'm thinking, "for a small 2 barrel derringer?"
He then asked about ammo, was told where he could find some, and went off and came back with a small box of 5 rounds of .410.
Clearly, if he remembers how to open it, he'll load 2 rounds and think he's good to go.
I'm thinking he'll never practice with it, and if he ever has to pull the trigger, he'll miss and scare the hell out of himself in the process.
Thought it would be good for the LGS to have someone (like me) to coach him a bit about what he should do, as well as sell him a gun.