Identification guide for designs of United States stamped envelopes, wrappers, and letter sheets.

Identification guide for designs of United States stamped envelopes, wrappers, and letter sheets
three and one-tenth cents

There is only 1 design of an indicium whose face value is three and one-tenth cents. It is:

3.1 c
USA authorized
nonprofit
organization

design U135

You have identified design #U135, diagnostic for
Scott #U589 (printed in ultramarine on white paper).