Pete, in this case the abbreviation "NSF" stands for "No Shoulder Fold" (and "SF" naturally means "Shoulder Fold"). Basically, the Canadian Mint released two versions of the queen's appearance that year. The NSF version shows the queen with a 'bare' neck/shoulder, while the SF type shows a curved line from the back of her neck to the top of her shoulder.
There are lots of posts with abbreviations on this site that I have trouble understanding too; so I've learned to check the "Glossary" that's available in the "General" category on the left side of this screen. It's helped me quite a bit with posts that interest me.