Sans & Streiffe 311, 312 and 313

These rules, as other brands distributed in the USA, were manufactured in Japan by the Ricoh Ltd company since the mid 1950's until the late 1960's. I estimate these years because I have not yet found any precise reference or catalog. As most of the rules produced in Japan, these were fabricated with bamboo coated with white plastic where scales were engraved, hold with metallic frames, and all plastic cursors screwed to plastic frames.

It seems that Sans & Streiffe Co. was mainly optical (cameras, binoculars, microscopes, telescopes, lenses, etc.), as well as drafting instruments, and it seems that slide rules were only a small branch in their production, because under this brand were commercialized only four slide rule models: the System Rietz model 310, and the log-log duplex models 311, 312 and 313

Designed for Science and Engineering applications, the log log duplex 311 (12.5" long - 10" long scales) has 21 scales: LL0, LL00, A [ B, K, CI, C ] D, S Cos, ST, T Cot on the front face, and L, LL1, DF [ CF, CIF, CI, C ] D, LL3, LL2 on the back face. This rule is identical to the Ricoh 150 Duplex Decitrig Log/Log, and to the Micronta 151, among others.

Models 312 and 313 have both the same 25 scales set: LL0, L, A [ B, S, ST, T, C ] D, DI, P, LL0 on the front face, and LL1, LL2, LL3, DF [ CF, CIF, CI, C ] D, LL3, LL2, LL1 on the back face. Model 312 is the longest of the family (14" long- 11 inches scales), identical to the Ricoh 151, and the model 313 the pocket size rule (6.6" long - 5" long scales). Model 312 is identical to the Lutz 151P Multilog. the Lafayette Decima-Log, and the SIC-1510 Astrolog, among others.

According with the serial number engraved on the edges of these specimens, the 312 rule was manufactured in 1964, the 313 rule in 1969, and the 311 rule in 1971. The 311 model was one of the first four rules my collection began with.