I wish I was smart enough to figure out how to make these links LIVE:
http://www.odcmp.com/Services/Rifles/index.htm
copy and paste this into your browser, it will take you right to the CMP website. Click on M1 Garand and it will describe the different grades and the prices of each grade.
I will tell you my own fairly recent experience. I purchased 1 "Collector" grade H&R Garand, and two "Correct" grade H&R Garands.
All three are about as new as you could possibly imagine a 50-60 yr old rifle to be. The Collector grade was about a 99%, a few dings and dents in the wood....PERIOD. Metal finish was like new. muzzle and throat erosion both guaged out at less than 1. I doubt the rifle had more than a couple hundred rounds thru it.
The two Correct grades......maybe 96% but only as far as the stocks were concerned, they both gauged out about the same, both less than 1 for muzzle and throat. A few more dings and dents in the stocks but metal finish was what I'd consider as 99%.
I don't know what your budgets are, but if your looking for premium NICE almost new M1's go with the Correct grade. I'm sure you'll be happy with the service grades as well. I feel like I tossed a few hundred bucks out the window comparing the Collector to the Correct. I might have just lucked out on the "Correct" grades.....it is the luck of the draw.
Either way, you can't loose. Its worth getting your paperwork together, and just doing it.
Trust me,
You'll be mighty glad you did!