Rulers related to typewriter and ribbon & carbon paper companies are a good sized category. Three of the ones listed here have calendars on them: How-Ko–1909/10 & Smith Premier–1910/11 and a Marchants Calculator 1959 calendar.  There are 21 rulers here and they are made out of 4 different materials: wooden, tin, celluloid and plastic. If the backside is not pictured, it means it is blank. They range in size from 5 1/4″ to 18″.

Marchant Calculators Ruler

R. C. Allen Ruler

Beaver-Panama Ruler

Muncie Typewriter Exchange Ruler

Blickensderfer Mfg. Co. Ruler

Eriksen’s, Inc. Ruler

Columbia Carbon Co. Ruler

H. & M. Ribbon & Carbon Co. Ruler

Marchant Calculators Ruler

Rapid Addressing Ruler

Ditto, Incorporated Ruler

Old Dutch Line Ruler

Central Valley Ruler

J & T Kabella Co., Inc. Ruler

How-Ko Ruler

Mittag & Volger Ruler

Noiseless Typewriter Co. Ruler

Panama-Beaver (plastic) Ruler

Panama-Beaver (wood) Ruler