It appears that M14 x 1.75 is a non-standard size-pitch combination. (it's usually 1.5 or 2 pitch). You should be more concerned with the pitch diameter and/or major diameter of the plug gage, I believe. While I couldn't find the direct answer to your question with my few minutes of browsing through the standard (that I've not looked at in years), I can recommend doing either of the following:
1. Simply send the gage to a qualified (read 'accredited') lab that handles dimensional work with thread gages. You'll get the tolerance... just make sure they are following ASME B1.13M
2. Ask the manufacturer, who's name should be enscribed on the gage. They made it and had to have checked it before it left their factory.