That MRE is old notice dark brown bag, dark brown bag MRE's have no heater inside them and not produced after the mid 90's.
shelf life chart is here on this link (Note this is not a real MRE retailer its in CHINA, just has the real chart from the army RND site.)
http://www.militaryfoods.com/mre_shelf_life.htm
If your going to buy MRE's buy the light tan ones that look like this:
http://static.howstuffworks.com/gif/mre-20.jpg they are newer and should have the heater inside.
As you can see from the chart its buyer beware, before you eat one give it the smell test. but you should be safe with the new light tan MRE's