To me, the lettering and logo don't look like anything Shell Oil has used in the past. Makes me suspect the sign.

Shell logos and signs:
https://www.oldgas.com/forum/ubbthreads.php?ubb=showflat&Number=80917

I'm not an expert. You can have a sign authenticated or appraised by experts for a fee at:
http://pcmpublishing.com/shop/products.php?cat=11
https://matthewstac.com/home/

Jim "Oldgas" Potts
Your host and moderator