Two (2) Swiss Rechenwalzen Cylindrical Slide Rule Calculating Drums, including one (1) National System Billeter Modell No. 10 and one (1) Daemen, Schmidt & Co. Loga. Both comprised of varnished paper scales on a metal cylinders with sliding, slotted cylindrical cages secured by aluminium rings with knobs, Loga with small clear celluloid indicators attached to the slats, all mounted on aluminium support stands. National System Billeter with maker's marks to drum and ring, Loga with maker's marks to drum and stand. Includes one (1) three page photocopy of the United States record for the Logarithmic Calculator by Julius Billeter, Zurich, Switzerland, dated January 23, 1894, one (1) one page photocopy of a Swiss article about the Loga-Calculator, dated January 1997, and one (1) photocopy of a pamphlet titled Professor Fuller's Calculating Slide Rulers, by Geirge Fuller. Drums range in size from 18 1/2" W x 6 1/4" dia. to 23 3/4" W x 6" dia. Overall dimensions range in size from 9" H x 22" W x 7" D to 9 1/4" H x 25 1/4" W x 8 1/8" D. Both items second quarter 20th century. Note: The Loga calculating drum does not specify a model number, however its measurements mostly closely correspond to the 15m. Provenance: Private West Tennessee Collection. CONDITION: All items in overall good condition with surface wear to varnish paper and metal to be expected from age and manner of use.