Master Slide Interlocking Rule Vacuum Oil Co. Rare!
This is an interesting advertising rule, featuring the sliding extensions, instead of the more common zig zag folding type rulers. The one is marked "INTERLOCKING MASTER LOCK RULE N.Y.C. APPRD. MADE IN U.S.A. VACUUM OIL COMPANY GARGOYLE MARINE OILS ROCHESTER, N.Y. U.S.A.". There is a patent mark also, "PAT'D 12/13/1910 PAT'D 7/29/1913". It also has inside, and outside measurement sides of graduation. The side marked "INSIDE" is confusing to me, as it start at the left with a section graduated from 1-8" then the next section from the left is marked from 60" down to 9". On the side marked "OUTSIDE" the graduations are from the left 0-60". This rule is in good working condition, all the brass locks hold well, a few sections have some minor warping, and there is a few small areas chipped, but still strong, and very useable. A rare advertising rule!