Originally Posted by Andy M.
If the recipe is for a prepared mustard (like Grey Poupon or French's), a full can of powdered mustard would be reasonable.
As promised, here is the recipe as found on the web for Special Mustard:
2 cn (2 ounce) Coleman's dry mustard
1 c Cider vinegar
3/4 c Sugar
Mix mustard and vinegar: cover, and let stand overnight at room temperature. Next day, beat eggs and add sugar. Combine sugar/egg mixture with mustard in the top of a double boiler. Cook, stirring, until desired thickness, about 4 minutes. Put in jar and keep indefinitely in refrigerator.
It does appear that you are correct about your assumption that a can of mustard powder is not an unreasonable amount to be used in the recipe. GrillingFool has contacted me and told me that he was able to find the abbreviation on the web and confirmed that it is used to mean 'can'. So it seems as though my problem has been solved, it just remains for me to thank you for your help, so thank you very much, it is much appreciated.