Era: 1873 ~ 1886 period
The arcuate on Levis 125 model in 1873 were stitched in straight alignment. The 6 stitches per inch technique were used.
Era: 1890 ~ 1928 period
The " Jacob " arcuate were aligned more to the right. The " wing " on the right side is higher too.
Era: 1942 ~ 1944 period
During the World War II period, changes are made in order to conform to rules set by the War Production Board for the conservation of raw materials. The Arcuate stitching design is removed as the thread was solely for decorative purposes only and not vital to the usefulness of the garment. In order to keep the design on the pants, LS&CO. sewing machine operators painted the arcuate in orange on each pair. A pair of Levi's without any noticable sign of arcuate is usually from this peroid. A pair in pristine condition with the paint still attached are quite valuable and can fetch thousands of dollars from ebay or a collector.
Era: Mid 1950s ~ present period.
Double needle machines were used to stitch the Arcuate design, resulting in the "diamond" effect and rendering each Arcuate identical. In the 60's, Levis changes stitching technique from 6 stitches per inch to 12 stitches per inch.