I *think* if you scan actual size and print from the photo manipulation/scanning package directly, it will print actual size. The dpi figure is irrelevant in this case, as it will simply alter the definition of the image, not its size.
This is also true if you import the image into a decent typesetting/layout program that measures objects in standard linear units (i.e. millimetres or, if you must, inches), such as QuarkXPress or InDesign. Again the dpi is irrelevant to the linear size of the imported image. In other words, if you scan a 25 mm-diameter coin at 100% and import it at 100% into Quark etc., it will appear 25 mm wide on screen (at 100% view, obviously) and in print (ditto).
However, lesser programs, such as those perpetrated by Microsoft, tend to import images based on the dpi figure, automatically resizing them so that they appear on screen at 72 dpi. For a program that is intended for use only on screen, such as PowerPoint, this isn't too much of an issue, but for Word, and that abhorrent abomination to humanity that is MS Publisher, it's a right pain in the rear. You then have to resize as best you can using the rulers.
I would imagine that SCWC is typeset using a typesetting program, not a word-processing program, and that therefore if you provide an actual-size scan, they'll be able to import it at actual size.