Relax, it looks OK for an M1862 Dreyse. The M1871 sight is much longer, mounted on a saddle (not a dovetail), with an extra "window" in the sliding leaf, and the back flip-up leaf is shorter, reflecting the flatter trajectory and longer maximum range. Clearly derived from the Dreyse sight, but not the same.
Both sights can be seen on P. 138 of "Deutsche Militärgewehre - Vom Werdergewehr bis zum Modell 71/84", which describes the development of the M1871 in some detail.
As to Dreyse spares ... think hens' teeth!