Beacon battery replacement


I wish to replace the batteries in the 3 estimote beacons (unsure where they are location or proximity ones) that I have. The box says Developer Preview Kit Bluetooth Low Energy Beacons and underside of each beacon states the version as Rev.D3.4.

The beacons dont appear to have any slots to easily open and feel I the only option would be to cut them open with a knife. I don’t wish to do that as I believe it cannot be resealed and it will lose its waterproof feature.

Any suggestions what my options are here and what batteries do these beacons take please?