The chrome is typically thicker and more lustrous than say an early 50s Phantom. The knurling on the rims isn't as uniform though and I think the Schwinn Tubular S-2 stamps stopped some time in 79. If you are worried about paint, I would avoid red in 77 and 78. The red ones I've had got crispy after so much exposure to the sun. The Blue 78 I have has a lot of scratches, but doesn't seem to be suffering the same scaley/flakey fate as the sun faded red 77 I had. That's not to be said that you can't find one with minty red paint. The screens like on the fork and chain guard are extremely easy to damage and wipe off if you get them wet or use any sort of cleaner, wax, or solvent on them. Decals can be sourced though. In 1981 they began to make models with both handbrakes instead of the drum if that is your preference. My black 81 is suffering from a burst cable. I haven't started on the project yet though.
View attachment 2131273 Thinking about fabricating my own cable ends out of something not plastic if I can't find a good cable cheap. Positron cables, silk screenings, and crispy original tires are the usual weak points you find on these bikes. Otherwise parts can be sourced. Brake shoes and drum hubs will likely always be high priced though.
Something interesting about the Positron derailleur, if the cable fails, you aren't stuck in high gear. It has detents built into the derailleur and you can still manually select what gear you want...leaves you in a lot less of a predicament.