Exterior storm windows have been around since the 18th century and became common at the end of the 19th century.
To the right is a page from The Mulliner Catalog of 1893. Here wood storm windows are available to match the window sash design. Click to enlarge.
2-1/4 inch stiles are standard but 3 inch stiles are available. Stiles are the vertical boards on each side of the storm window.
Storm sashes were 1-1/8 inch during the time.