Nurdler

Hi, I have just registered with this site as I have been researching some old Weetabix Lego and wanted to learn more. My Father worked for Weetabix and as a kid we were fortunate to play with all the promotional sets including the Weetabix Castle set from the early 1970s. Up in the parents loft we found a few boxes that are unopened, and complete including a windmill and some houses and a whole village set (I think) still sealed in the Original brown cardboard packaging. The box is completely blank except for a red Lego logo and numbers on the brown paper seal are as follows - 03/29058 and 1X 1589. I dont want to open the larger box as it is still sealed which is very rare Im told. Can you please identify what I have please? Many thanks Nurdler