S# 2,861 - Model 1858-E ("Series II") movement, circa 1860-61, with Type E plates, compensated balance, Mershon's patented compound regulator, and 15 jewels in screwed down settings. Screwed-down settings (for the visible jewels only) are extremely rare in this S# range, and Mershon's regulators are at least scarce. While the level of adjustment is not engraved on the plate, and the factory records for this S# no longer exist, it is likely that this movement was adjusted at least to temperature as well as to isochronism, and possibly even to 6 physical positions.
