The Milwaukee Road indeed has a long history of date nail use. They used steel nails in the early years (1908-1910) most had a letter with the year indicating the type of treatment used on the tie. A few of the letters used have not been deciphered. They stopped using nails (1910-1927) when they started using the small copper nails. They used these from 1927-1942 and 1946-1951). Also in 1962 they used a nail in test tracks in Iowa. During the 1930-1934 period they also used small steel nails and in 1928 used a steel Z28 indicating a zinc treated tie. Dates on the nails prior to 1930 were indented. Those after were raised.

They did use nails in catenary poles, but these were square nails.
Regards,
Rolland