What’s the best way to preserve a forty year old almost factory shine trap that way? I’ve been doing a light coat of WD 40 on some that don’t look as new. Thanks

WD-40 is okay for cleaning traps but it seems to dissipate after time. Small engine fogging oil lasts longer but is sticky.
For a shiny trap you might consider some kind of floor or furniture wax...

Ren Wax - best stuff out there. I use it mostly on guns that stay in the safe and collector knives but have used it on the few shiny traps I have. It costs about $10 a can but will last you for years. Dries fast and clear and you only use a little bit. It's pretty tough too. Put it on once and you're done.

Ren Wax available at Lowe’s?

Not sure about Lowe's. I bought mine online a few years ago- just checked amazon and they have it but it's $15 now for the smaller can and $25 for the size in the picture so I guess it's gone up. Still not bad, you'll only need one can. I probably haven't used 1/4th of mine since I got it.