Ok you can laugh if you want to (not the thing between ones leg,see above), but years ago I bought a tool from the Gorilla Tool Company LLC. called "THE GORILLA TOOL" not the Gorilla ***** for some of you!
That tool is fantastic if it has any downside it does not check for any size under 1/4" for machine screws. That tool comes in either sae/or metric and it will last forever even under the worst environments,it will tell you the bolt size,the thread pitch,what wrench to use and the bolt grade. Everything is marked in large numbers making it easy to read (for us older guys)and it fits into your shirt pocket.
I seem to recall that I bought it from MSC and it is not cheap,but I can tell you that this tool is all made of SS and it is built to withstand anything and it is made in the USA.