I recently purchased a complete 1935 6 1/2 set with skyscraper. It came with a small bottle labeled 3 in one oil sample. Did this originally come with this set? I have never seen one. if it did, is there other sets that it came with?
Yes, starting in 1933 Gilbert included this in large box sets that came with a motor. It was a small, corked glass vial of 3-in-One oil. It came wrapped in a small instruction sheet that indicated it was a free sample and gave directions for oiling the motor. The oil appears in all sets with electric motors through 1938 and in the Electrical Train Set through 1942.