Certainly this was a postwar measure to provide an opportunity for service personnel to vote. The 1919 statute also provided absentee status for students, "any officer or employee of the United States or of this state" and "commercial travelers."
This article from the Oregon Journal, October 25, 1920, 2, indicates that 42 people had applied for an absentee ballot; by election day this had swelled to over 100.
Portland city ordinances provided for voting machines in 1919 but it does not seem that they were a feature of this election.
