It looks like you're looking for a download link related to — but I couldn’t find any legitimate or official source for a font with exactly that name.
If you are looking for a download link for this font, it is usually distributed as a file compatible with CAD software (often as an .shx or .ttf file): stdx603fontdownload link
.exe for a fontOften refers to the "Standard" version of a font family, distinguishing it from Pro (which includes more glyphs) or Light/Bold variants X (Experimental/Extended): "stdx603font" It looks like you're looking for a
However, it is highly likely that "STDX603" is , but rather a file code, a cryptic filename from a zip archive, or a licensing code used by a font distribution site. Unverified “free font” websites with pop-ups Torrent or