There's a sticker in the photo which has the serial number. I can't read it = even zoomed in = but if you post it, maybe you can read it on your og photo, we can help.
Yes, it is a Grandee. I have a Vista just like it sitting in my front driveway right now - it came out of a deck with a minor leak. Leak fixed, people bought another tub and I am now the owner!!