This unmarked 5-1/2" wooden right triangle has angles of about 30° and 60°. The corners of the instrument have broken off, and some drawing triangles were neither 30°-60°-90° nor 45°-45°-90°, so it is not possible to know the original dimensions of the object. (For triangles with other angle measurements, see 1990.0690.01 and MA.323412.) Users held the object in place by putting their thumbs in an 11/16" circle cut from the center. Compare to 1979.0876.02, 1983.0238.01, and MA.304826.137.
The dating of other objects from this donor suggests the triangle was made around 1900. The Eugene Dietzgen Company sold a 5-3/4" 30°-60°-90° cherry triangle for 8¢ in 1904, while Keuffel & Esser offered a triangle with the same dimensions but in pearwood for 10¢ in 1909.
References: Catalog of Eugene Dietzgen Co., 7th ed. (Chicago, 1904), 194; Catalogue and Price List of Keuffel & Esser Co., 33rd ed. (New York, 1909), 223.