If it doesn't have the name Darne, or Halifax on it, it 'ain't a Darne. Period. If it has a one piece stock, it is typically an 1894 patent gun, as opposed to Regis Darne's later 1909 patent guns, which contained several improvements, stylewise and mechanically.
Clone is a pretty good term for the whole mess of sliding breech copies, since they all spawned from the fertile mind of Regis Darne, who could well be called France's J.M. Browning. Most of them are well made. I wouldn't get too shook up about what name was, or wasn't on it. Either shoot 2 1/2 inch ammunition in it, or have the chambers lengthened, and go use it. It isn't worth a fortune, and, if they fit a guy, they are super bird guns.
Enjoy.
Best,
Ted
