Was walking past Marayong Woolies where i saw these posters up around the walls and everywhere.
I got a pretty low-res picture (on a nokia), here, and have recreated it in MS Paint to a higher-res, which is the one in the bargain link.
I am not sure if it is for multiple stores. The one that i went to (Marayong) had these posters even on Woolies' outside walls, and had a little id code down the bottom of the poster saying "Special 22/12-24/12", and nothing specifically saying Marayong. Hope that helps. If anyone does see this at other stores please mention. See edit.
Edit:
According to comments, It does seem to be Nationwide. Enjoy your Christmas ham!
Advertised in the paper in WA today as well.
Good work recreating the ad in MSpaint!!