The M in IMR stands for manganese and is an inherently safe chemistry, ie much less prone to blowing up. What little I know about batteries is this: the IMR batteries are relatively safe but give less juice than some other types like ICR, BUT they can be drained faster without problem, great for big lasers. they aren't protected like ICRs, but their chemistry means overcharging is hard and as it's a safe chemistry it's unlikely a good battery will go unstable.
That green battery you got looks like one of the many Chinese cheapies, I have about 8 AAs just like this from garden solar lights, some of them say "grepow battery" in them and googling that company immediately leads back to china. It's probably not particularly beefy but as long as the sleeve isn't lying about it being IMR you should be good to go.
I personally use a test meter on my batteries to make sure they haven't overcharged before inserting them to a laser. Multimeters are pretty cheap so it's worth getting hold of one.
