A very rare find, Graphoplex 612 engineering slide rule with Schlumberger corporate branding

Made by Graphoplex, Paris, France
Corporate Issuer: Schlumberger Instruments — Sefram Division (France)
Date: c. 1965–1975

This slide rule is a factory‑produced Graphoplex 612, a professional model widely used by engineers during the mid‑20th century. The instrument carries a printed Schlumberger logo, consistent with the branding used by Schlumberger Instruments, the European electronics and test‑equipment division of the Schlumberger group.

During the 1960s–1970s, Schlumberger Instruments issued branded technical tools — including slide rules — to laboratory staff, field engineers, and customers involved in electronic measurement, calibration, and industrial instrumentation. The French Sefram division, operating in the same country as Graphoplex, is the most probable source of this particular example.

The presence of the original brown leather case marked “612” further supports authenticity and indicates the item was supplied directly through Schlumberger’s engineering channels rather than retail distribution.

Examples of Schlumberger‑branded Graphoplex slide rules are rare, as they were produced in limited numbers for internal use rather than commercial sale. Surviving specimens with intact logos and original cases are considered desirable among collectors of scientific instruments, slide rules, and Schlumberger memorabilia.

This example is in excellent condition, the cursor slides freely, both it and the reticule are clear and unmarked. There are a few very light scratches on the back of the rule, consistent with light use.

The original leather case is still supple, the stitching along one edge has come away and there is wear and tear in a couple of places, but overall it has a lovely patina.

I collect vintage slide rules and this is one of the nicest 612s I’ve seen, the Schlumberger logo makes it a very special piece.