karlok:
I already also heard, that the batteries are a bit more than 1.5V, maybe 1.6V or 1.7V. A new "1.5V"-battery I measured had a bit more than1.6Volts. That means that 1.6V*3=4.8V should be definitely still in the acceptable range for the laserpointer. Most of them are from China and hence don't have a manual with technical parameters.
Yes that's very true, and always something to keep in mind when working with batteries. The datasheets always go by a nominal voltage though the "name brands" usually will have plotted voltage curves available as well. Therefore on any battery powered device design you need to ensure the total voltage of the pack can provide a high enough voltage until the cells are mostly discharged, while making sure fresh batteries won't cause the excessive initial voltage to the device being powered.