How do I *accurately* (n.nnnn) measure very small hole diameters?

What size is a very small hole ? We jig holes .02900 Diameter
holding .0001 tol. on the diameter and .0001 on location.We check them using
lapped gage pins on a Moore inspection machine.The hole has a very good grind
finish but not good enough for checking with the gage head that reads in
..00001+or-Our coustmer checks them to + or- .000035 This is a series of holes
with a pin in them.This pin has a hole in it and thats what is held to the
..0001 tolarance. These are gages to check pin locations on gold plated plugs
that are used in a wepon system. Ray Mueller