Remington (made by Butler) Lord&Lady Derringer?

[Darto]

Were these made at a time when they would be old enough to be considered C&R?

In other words, All of them are C&R, none of them C&R, some of them C&R?

The ones I see are .22 Short only.

[TRAP55]

Butler built these for Colt, not Remington, and they were all made in .22 Short.
The ones made from 1959 to 1963 have a D or N suffix in the serial number.
Starting in 1970, the suffix was DER.
There were non-firing versions with no serial number, and some of these have been reported to have serial numbers ending in DER.
In my opinion, none of them should be fired. Frames and barrels are made from pot metal, and the rifling is cast into the bore. It doesn't take many rounds to make it a smooth bore, but they usually start falling apart before that.