Valuing Stamp collection -br

I inherited a substantial stamp collection from my grandfather. A good bit are just loose stamps in a shoe box, but the remainder are filed and catalogued. There's a lot of stamps from countries outside the us, especially a good bit related to his tours during WW2. The collection is just too much to try and showcase, and is starting to deteriorate due to age. Anyone know someplace in br area that can determine what if any are valuable, so I can keep a few examples to display then sell or donate the remainder?