Reportedly, 4,500 of these transitional "Model 1877" carbines were manufactured between 1877-1878, with approximately 2,500 manufactured in the first half of 1877 ending around serial number 76725, and another 2,000 manufactured in the first half of 1878 ending around serial number 89729, with some changes noted between these two production batches; most notably the rear sights, differences in the finish of the breech blocks and markings on the breech blocks and locks (reference lot 275 auction 89). Manufactured within the correct serial number range, with a high-arch breechblock, standard blade front sight, notch and folding ladder rear sight graduated to 1,200 yards with stepped base, standard three-groove rifling, "MODEL/1873/(eagle head with crossed arrows)/U.S." breech block marking, eagle and shield motif and "U.S./SPRINGFIELD/1873" on the lock with a three-click tumbler, single stacking sling swivel on the barrel band, smooth trigger, saddle bar and ring on the left, crisp circled script "ESA/1877" inspection cartouche of Springfield Master Armorer Erskine S. Allin stamped on the left wrist of the stock. The stock has a thick wrist, a 10 1/2 inch comb and a trapdoor compartment in the butt.