It looks like the path of least resistance leads to Microsoft fonts.
In more recent revisions of software packages, the TrueType font ISOCPEUR reliably reproduces the original drawing board lettering stencil style, however, many drawings have switched to the ubiquitous Arial.ttf. However, with the closed four, and arced six and nine, romans.shx typeface could be difficult to read in reductions.
When CAD drawings became more popular, especially using US American software, such as AutoCAD, the nearest font to this ISO standard font was Romantic Simplex (Roman) - a proprietary shx font) with a manually adjusted width factor (over ride) to make it look as near to the ISO lettering for the drawing board. The best website for free high-quality Arab Shx Autocad 2013 fonts, with 25 free Arab Shx Autocad 2013 fonts for immediate download, and 2 professional Arab Shx Autocad 2013 fonts for the best price on the Web. The ISO character set (font) has a seriffed one, a barred seven, an open four, six, and nine, and a round topped three, that improves legibility when, for example, an A0 drawing has been reduced to A1 or even A3 (and perhaps enlarged back or reproduced/faxed/ microfilmed &c).
Note: Windows XP and Vista systems require going to the Control Panel and opening Fonts and then using. TTF files do not go into AutoCADs own Fonts folder. The stroke thickness is related to the character height (for example, 2.5mm high characters would have a stroke thickness - pen nib size - of 0.25mm, 3.5 would use a 0.35mm pen and so forth). AutoCAD reads TrueType (.ttf) fonts that are installed in the operating system. ISO Lettering templates, designed for use with technical pens and pencils, and to suit ISO paper sizes, produce lettering characters to an international standard. Lower case letters are rare in most drawings of machines.
Engineering drawings use a Gothic sans-serif script, formed by a series of short strokes. With the goals of legibility and uniformity, styles are standardized and lettering ability has little relationship to normal writing ability. It is used to describe, or provide detailed specifications for, an object.
Technical lettering is the process of forming letters, numerals, and other characters in technical drawing.