I think I have come across a Trapdoor Cadet in 50-70. Here is the data:
Length 48 7/8
Barrel 29 1/2

Serial number on breech and barrel do not match.

The ramrod is the in the stock
Bayonet is 19 inches
no swivel on the trigger guard
Lock dated 1863
Breech block date 1870
There is no spoon in the stock for the ramrod.

Are there any defining characteristics to confirm that it is fact a 50-70 cadet.