The EPS file type is primarily associated with 'Encapsulated PostScript'. There are two distinct types of .EPs files, one of which is a vector based graphics file and can be opened and easily edited for type, color, etc. in Adobe Illustrator or PC vector based programs like Corel Draw. They can be CMYK color, or flat pantone color based. These files could be "placed' or "imported" into Pagemaker (or Word, Quark, etc.), but not opened by it. They can be almost infinitely scaled in size without degrading the output because they are vector based. The other is an .EPS photo file, flattened, set resolution "picture" type file.
It can be opened in PhotoShop or other image editing programs, also placed or imported into Pagemaker (or Word, Quark, etc.), but it will be significantly degraded if scaled beyond the set resolution. These are usually CMYK files, or can be set as Pantone duo-tone, tri-tone files. The initial characters for the EPS format (C5 D0 D3 C6) only works for DOS EPS files. A better magic value (initial characters) may be "%!PS" (25 21 50 53). %!PS does not always appear at the start of the file (though for Unix's ps2epsi it does), but should appear near the start of the file. It should have a version after it, e.g., "%!PS-Adobe-3.0 EPSF-3.0".
PhotoShop or other image editing programs
MIME type : application/postscript, application/eps, application/x-eps, image/eps, image/x-eps