French Steel

These two slide rules are made from polished heavy sheet steel; possibly plated, but I don’t think so. The scales and other writing are engraved into the steel. The rules are similar, but not identical.

From the writing on them one can see that they are advertising French companies. I believe some of the other language indicates they are of French manufacture, but I’m not sure about that. Perhaps someone out there knows enough French, and France, to tell me that for certain?

The “Paul Torche” rule seems to be advertising old electronic components (in English, static transformers and mercury vapor rectifiers). That would date it to about the 1950s or earlier. The other rule seems to be advertising abrasives; something I know next to nothing about. Other than those two flimsy clues, the only other thing that might help date them is that one of them (the abrasives rule) was coated with a substance that I believe was very old “cosmoline”. I’m quite familiar with that stuff from my days in the U.S. Navy; lots of stuff came packed in it. Cosmoline was a petroleum-based product with the consistency of heavy grease, and often it was green in color from the cuprous oxide in it that discouraged any life form from attacking whatever it was protecting. This was very important in places like the tropics, where they have bacteria and fungus that can eat just about anything. Anyhow, this rule was coated with what looked like hardened Cosmoline. I’m sure it was petroleum-based, because soap and water barely touched it, but Nevr-Dull sluiced it right off. I’m thinking that the cosmoline dates it to no more recent than about the late 1950s, consistent with the electronics components. But…both the electronics components and cosmoline were in use as early as the 1930s (and possibly the 1920s), so that’s still a broad range.

Any ideas, anyone? Please leave your thoughts in the comments…