what is the Seer Rating for Proline XE SL model GS6-75-YRVHTL

Hi Mike, for specific questions about products, you will have to contact the brand directly.
You can find their contact details here: https://www.hotwater.com/about-us/contact.html
And here is a link to the product's information page that might be helpful too, although I don't believe it lists the Seer rating: https://www.hotwater.com/products/power-vent-proline-xe/gpvx-75l-310/100310836.html