So you think this bike is mostly original equipment and not an aftermarket refurbish job? I can't imagine an original 3-speed with fenders and chainguard from the (50s, 60s, 70s?) being as light as you claim. I've got a 1955 Raleigh 3-speed and it ain't light. The frame is heavy steel, original rims were steel, bars, stem, seatpost all steel. Curious to see what you find out about this bike.
Oil is good, grease is better.
2007 Peter Mooney w/S&S couplers/Terry Butterfly
1993 Bridgestone MB-3/Avocet O2 Air 40W
1980 Columbus Frame with 1970 Campy parts
1954 Raleigh 3-speed/Brooks B72