Have you tried taking it to your local hardware store?  My hardware store has a really neat tool that identifies but and screw sizes.

I recent,purchased a vintage 2-8-0 Reading.  I need to remove the valve gear and side rods from the drivers so that I can re-quarter 2 drivers. It looks like the bolt holding the valve gear is small than the bolts holding the siderods.  Does anybody know what size bolt those are?  Are they metric?

I have a Bachmann Texas & Pacific 4-6-0 HO scale locomotive.  I'm in the process of adding a sound decoder.  I'm looking for the wires for the headlight (white and blue).  the wires in the tender are all black.   Would the terminals labeled L+ and L- be for the blue and white wires respectively?   I'm assuming M+ and M- is for the motor.

Dave