There’s a picture on page 138 of John Underhill’s 3rd Scott selection of what I think is a machine identical to yours. This uses the single down tube frame and has what is described as a ‘chromium plated tank of welded construction of similar shape to the TT Replica’. I’ve recently purchased a Flying Squirrel of the same year but the tank has long since been painted and I’ve not had the opportunity to dig under the paint to see if there was ever any plating. Any plated parts on my machine are chromium rather than nickel although I’m uncertain how much of it is origional. My machine is, I think a flying squirrel de-luxe with Scott forks and originally had a lighting set although all that’s left of it is the magdyno.
Hope this may be of help