Mascot & Monitor Circular Slide Rule

Mascot circular slide rules were commercialized by the based in New York company Tavella Sales Co., an importer and seller of scientific instruments, including Gilson instruments, from the early 1930's until the early 1950's (?), assumed years made based on advertisements and documents found from this company. There are some Trade Catalogs in the Smithsonian National Museum of American History, but they don't give any information of the company operation years.

I did not find information about the specific manufacturer of these rules, only the copyright year, 1934, is printed on the rule. The little instructions leaflet does not have any year or even a reference to Tavella Sales Co. This rule was fabricated in two sizes: 6.26 inches, labeled Mascot & Monitor, and 2.75 inches, labeled Mascot Vest Pocket.

Fabricated all plastic, assembled with two concentric discs and a clear cursor, all pivoted at the disks' centers. Scales were printed in both sides: L, C ( D, DI ) on the front face, and S, A, C, T on the back face. Scales are not labeled except the Sine and Tangent scales; these trigonometric scales are given in degrees-minutes. This could be considered a slide rule for students and professionals.

No information other than copyright year is on the rules, nothing about the fabrication year, I found only magazines' advertisements published between 1944-1945. We can assume that these rule was fabricated in the lapse 1935-1945:

Click on the next links to see professional panoramic pictures of the Mascot Vest Pocket and User Manual:

https://www.sliderulemuseum.com/Circular/Mascot_Vest_Pocket_Slide_Rule_1934_TavellaSalesCo.jpg

https://www.sliderulemuseum.com/Manuals/ISRM_M288_Mascot_Vest_Pocket_Slide_Rule_Instructions.pdf