I am uncertain what this poster is exactly. I was only sent a scan of the poster. It appears to be similar to either the Regular or the Advance C: (It is difficult to tell from the scan whether or not "Coming this Christmas" or some other advance text exists at the bottom):

However the entire bottom fourth is a red color, something not found in any other Dune posters. I would love to call this a newly discovered "Advance D" but the poster is reportedly only 24 x 36 inches. This would make it highly unusual for an original theatre poster. I therefore suspect this is a commercial reprint.

Any further information would be greatly appreciated.