Underwood typewriters are quintessential antiques among collectors. These machines were made in the millions in the early 20th century. Underwood No. 1 and No. 2 models are less common than the classic Underwood No. 5. If you have bought an Underwood typewriter or are considering adding one to your collection, you'll want to figure out exactly how old it is.
Look at the typewriter's back panel. If it says "Wagner Typewriter Co.," it was made between 1895 and 1900 and is a No. 1 or No. 2 model. Because these models are the oldest and only 12,000 were made, they are the most valuable.
Determine if your typewriter has an open or closed frame. If it has an open frame, you'll be able to see the inner workings. If it has a closed frame, the workings will be covered by sheet metal. Open-framed typewriters date from 1900 to the 1930s, while closed-frame models are from the '30s onward.
Look at the rows of keys on your model. Portable typewriters, which were slightly smaller, can be dated by their keys. If your portable model has three rows, it is from 1919 to 1929; if it has four rows, it is from the '30s or '40s.
Check the serial number under the typewriter's carriage. For example, serial numbers 100, 1000 and 10000 are from 1900, 1901 and 1902.
If your typewriter was made in 1904, 1906, 1907 or 1908, the serial number will be 50000, 100000, 150000 or 200000. Serial numbers between 247500 and 450000 are from 1909 and 1912. Models made between 1913 and 1917 were numbered between 551000 and 940000, while models from 1918 to 1925 were numbered between 1050000 to 1910000. Serial numbers 2070000 to 3825000 indicate the typewriter was made between 1925 and 1931.